RESIDUE REVIEWS

VOLUME 28

RESIDUE REVIEWS Residues of Pesticides and Other

Foreign Chemicals in Foods and Feeds

RUCKSTANDS-BERICHTE Riickstande von Pesticiden und anderen

Fremdstoffen in Nahrungs- und Futtermitteln

Edited by

FRANCIS A. GUNTHER Riverside, California

ADVISORY BOARD

F. BAil, Berlin, Germany· F. BRO-RAsMUSSEN, Copenhagen, Denmark J. W. COOK, Washington, D.C .• D. G. CROSBY, Davis, California

S. DORMAL-VAN DEN BRUEL, Bruxelles, Belgium C. L. DUNN, Wilmington, Delaware • H. FREHSE, Leverkusen-Bayerwerk, Germany

J. C. GAGE, Macclesfield, England· H. GEISSBUm.ER, Stein AG, Switzerland S. A. HALL, Beltsville, Maryland • T. H. HARRIS, Bethesda, Maryland

L. W. HAZLETON, Falls Church, Virginia • H. HURTIG, Ottawa, Canada O. R. KLIMMER, Bonn, Germany • G. K. KOHN, Richmond, California

H. F. LINSKENS, Nijmegen, The Netherlands· H. MAIER-BODE, Bonn, Germany N. N. MELNIKOV, Moscow, U.S.S.R. • R. MESTRES, Montpellier, France

P. DE PIETRI-TONELLI, Milano, Italy· R. TRUHAUT, Paris, France

VOLUME 28

SPRINGER-VERLAG BERLIN • HEIDELBERG • NEW YORK

1969

All rights reserved. No part of this book may be translated or reproduced in any form without written permission from Springer-Verlag.

ISBN-13: 978-1-4615-8454-4 e-ISBN-13: 978-1-4615-8452-0 DOT: 10.1007/978-1-4615-8452-0

© 1969 by Springer-Verlag New York Inc. Softcover reprint ofthe hardcover 1 st edition 1969

Library of Congress Catalog Card Number 62-18595.

The use of general descriptive names, trades names, trade marks, etc. in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone.

Title No. 6631

Preface

That residues of pesticide and other "foreign" chemicals in food­stuffs are of concern to everyone everywhere is amply attested by the reception accorded previOUS volumes of "Residue Reviews" and by the gratifying enthusiasm, sincerity, and efforts shown by all the in­dividuals from whom manuscripts have been solicited. Despite much propaganda to the contrary, there can never be any serious question that pest-control chemicals and food-additive chemicals are essential to adequate food production, manufacture, marketing, and storage, yet without continuing surveillance and intelligent control some of those that persist in our foodstuffs could at times conceivably endanger the public health. Ensuring safety-in-use of these many chemicals is a dynamic challenge, for established ones are continually being dis­placed by newly developed ones more acceptable to food tech­nologists, pharmacologists, toxicologists, and changing pest-control requirements in progressive food-producing economies.

These matters are of genuine concern to increasing numbers of governmental agencies and legislative bodies around the world, for some of these chemicals have resulted in a few mishaps from improper use. Adequate safety-in-use evaluations of any of these chemicals per­sisting into our foodstuffs are not simple matters, and they incorporate the considered judgments of many individuals highly trained in a variety of complex biological, chemical, food technolOgical, medical, pharmacological, and toxicological disciplines.

It is hoped that "Residue Reviews" will- continue to serve as an integrating factor both in focusing attention upon those many residue matters requiring further attention and in collating for variously trained readers present knowledge in specific important areas of residue and related endeavors; no other single publication attempts to serve these broad purposes. The contents of this and previous volumes of "Residue Reviews" illustrate these objectives. Since manuscripts are published in the order in which they are received in final form, it may seem that some important aspects of residue analytical chemistry, biochemistry, human and animal medicine, legislation, pharmacology, physiology, regulation, and toxicology are being neglected; to the contrary, these apparent omissions are recognized, and some pertinent manuscripts are in preparation. However, the field is so large and the interests in it are so varied that the editor and the Advisory Board earnestly solicit suggestions of topics and authors to help make this international book­series even more useful and informative.

"Residue Reviews" attempts to provide concise, critical reviews of timely advances, philosophy, and significant areas of accomplished or needed endeavor in the total field of residues of these chemicals in foods, in feeds, and in transformed food products. These reviews are either general or specific, but properly they may lie in the domains of analytical chemistry and its methodology, biochemistry, human and animal medicine, legislation, pharmacology, physiology, regulation, and toxicology; certain affairs in the realm of food technology con­cerned specifically with pesticide and other food-additive problems are also appropriate subject matter. The justification for the prepara­tion of any review for this book-series is that it deals with some aspect of the many real problems arising from the presence of residues of "foreign" chemicals in foodstuffs. Thus, manuscripts may encompass those matters, in any country, which are involved in allowing pesticide and other plant-protecting chemicals to be used safely in producing, storing, and shipping crops. Added plant or animal pest-control chem­icals or their metabolites that may persist into meat and other edible animal products (milk and milk products, eggs, etc.) are also residues and are within this scope. The so-called food additives (substances deliberately added to foods for flavor, odor, appearance, etc., as well as those inadvertently added during manufacture, packaging, distribu­tion, storage, etc.) are also considered suitable review material.

Manuscripts are normally contributed by invitation, and may be in English, French, or German. Preliminary communication with the editor is necessary before volunteered reviews are submitted in manu­script form.

Department of Entomology University of California Riverside, California May 28,1969

F.A.C.

Table of Contents

Insecticide residues in California citrus fruits and products By F. A. Gunther.................................... 1

Subject Index ............................................ 121

Manuscripts in Press ...................................... 128

Insecticide residues in California citrus fruits and products*

By FRANCIS A. GUNTHER\)\)

Contents

I. Introduction ................................................. 2 II. Residue legislation ............................................ 6

III. Tolerances .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 a) Establishment of tolerances .................................. 7 b) Pertinent insecticide tolerances for citrus fruits .................. 9

IV. Generalized insecticide residue behavior on and in citrus fruits ....... , 14 a) Degradation and persistence curves ........................... 15 b) Established persistence curves ................................ 34 c) Residue half-life concept .................................... 34 d) Uses of half-lives and persistence curves ........................ 39 e) Effects of variety on residues ................................. 41

V. Insecticide residues in citrus products ............................. 42 a) Citrus juices .............................................. 42 b) Laboratory-prepared citrus pulp cattle feed ..................... 47 c) Citrus oils ................................................ 52 d) Orange marmalade ......................................... 57 e) Dried and candied orange rind ............................... 58

VI. Insecticide residue removal by washing ........................... 58 VII. Systemic insecticides as residues ................................. 59

VIII. Some market survey insecticide residue data ....................... 64 a) The French program ....................................... 64 b) The California-Arizona Citrus League program .................. 64

IX. Multiple residue methods for citrus fruits .......................... 69 X. Developmental citrus residue-analytical methodology with fresh fruits.. 74

a) Presampling considerations .................................. 74 b) Sampling procedure ........................................ 76 c) Storage of fresh samples ..................................... 78 d) Processing of samples ...................................... 79 e) Storage of extractives ....................................... 92 f) The analysis .............................................. 93

• Presented in partial and summary form at the International Citrus Sym­posium, 19 March 1968, Riverside, California: see GUNTHER and WESTLAKE (1968) in "References" section .

•• Department of Entomology, University of California, Riverside.

1

2 F. A. GUNTHER

XI. Miscellaneous aspects and conclusions ............................ 96 a) Current insecticide dosages in California ....................... 99 b) Adequate developmental, surveillance, and

mOnitoring programs for pesticide residues ...................... 99 c) Insecticide metabolites and other alteration products in citrus fruits .. 101 d) Citrus insecticides in the grove environment ..................... 102 e) Deposition and persistence of insecticides on leaves versus fruits . . .. 106

Summary ......................................................... III Resume .......................................................... 112 Zusammenfassung .................................................. 113 References ........................................................ 114

I. Introduction

Prior to about 1945 it was not realized that spray and dust deposits of most organic insecticidal l chemicals penetrated, in the field, into subsurface regions of sprayed citrus fruits, even though they were generally nonsystemic in action, as with some of the DN compounds and rotenone. Also, emphasis on «residues" (deposits) prior to this same time was on correlations with pest-control efficacy rather than on safe consumption of the treated commodity, so that initial deposits and aged deposits were most often obtained as weight of insecticide per unit areas of leaf (foliage) tissue 2 rather than on and in mature fruits, as with sulfur, lime-sulfur, and lead arsenate, because insect popula­tions were usually evaluated on leaves or twigs rather than on fruits. In connection with the field performance of DDT and other new in­secticides against insects and mites in citriculture, however, it was realized shortly after 1940 that the slow disappearance or attenuation from leaves of these (DDT) surface deposits and effective residues from organic pesticides signified at least partial penetration into subsurface tissues (GUNTHER 1946 and GUNTHER et al. 1946). It was also im­mediately recognized (BOYCE 1946) that pesticides penetrating into leaf tissues would probably also penetrate into fruit tissues, and that these penetrated residues in citrus fruits, for example, could conceiv­ably constitute a new type of hazard to the consuming public. Atten­tion was therefore turned immediately to fruits and other edible plant parts as the residue analytical substrates, and correlations of deposits and residues with biological performance became of secondary im­portance as the pharmacological and toxicological significance of per­sisting and altering «residues" was recognized. Because of laboratory

1 The term "insecticide" often includes those chemicals used for mite control, or "acaricides." Both types of pest-control agents are considered as insecticides in the present report. Only the organic insecticides are included. Chemical designa­tions of insecticides mentioned in text are listed in Table XXXII.

2 See section XI d) for a discussion of deposits and residues expressed as p.p.m. (weight basis) versus p,g./cm.2 (area basis).

Insecticide residues in citrus fruits 3

convenience and presumed parity of public health significance, these values were now expressed on a part-per-million basis for all foodstuffs.

Residue chemistry and biochemistry as known today around the world were therefore conceived within the citrus industry, and the first true surface and subsurface residue evaluations were made with mature lemons and oranges in the Department of Entomology, Univer­sity of Califomia Citrus Experiment Station, Riverside. The term "residue" was coined to refer to aged and usually penetrated pesticide chemicals and their in situ alteration products, particularly on and within the edible parts of treated plants and within animal tissues. Thus, "deposit" now refers to pesticide chemical initially laid down by the field treatment, whereas "residue" refers to material on and in the plant part after the processes of weathering, metabolism, hydrolysis, penetration, etc., have begun and on (e.g., wool) and in animal parts. Additionally, chemical so located as still to be available to the pest is known as an "effective deposit" or "effective residue" depending upon both its age and its major location with respect to the plant cuticle; this terminology does not apply to animal tissues (GUNTHER and BLINN 1955, GUNTHER 1962, 1966, and 1968 a).

Federal legislation for control of food quality since 1954 [Public Law 83-518 et seq. and the Federal Insecticide, Fungicide, and Ro­denticide Act of 1947 et seq. (HARRIS and CUMMINGS 1964)] has dictated that tolerance assignments (legally permitted maximum amounts of residues) and classifications for pesticides on and in raw agricultural commodities shall be based in part upon particular formu­lations and particular dosages applied in the field, with specified tim­ing in relation to harvest or blossoming periods and to numbers and spacings of multiple applications if required. Acceptable residue in­formation and tolerance assignments are therefore commonly based upon extensive biological testing in the field with formulations thought at that time to be standardized and with dosages that would achieve the desired pest control. Subsequent significant changes in formula­tions and recommended dosages require reconsideration by the licens­ing and registration authorities, with probable reconsideration of tolerance assignment if dosages or frequencies of applications are increased or if minimum intervals to harvest are decreased.

Residue information developed in achieving legal commercial use of a pesticide chemical is therefore felt to represent the maximum residues that could actually occur in agricultural commodities at har­vest 3 if the label instructions on the pesticide container were strictly and consistently followed. Consequently, for every pesticide in every use on every crop plant there exist often abundant data (usually un­published) illustrating maximum and average residues that will result from good agricultural practice. If dosages, timing, formulations, and

8 Ergo, from "good agricultural practice."

4 F.A.GUNTHER

numbers of applications are not appreciably changed after legalized use is achieved, residues found in "market surveys," "market-basket studies," residue surveillance 4 programs, and residue monitoring II programs with a specific crop should reflect the original developmental data provided those original data were representative of the treated crop and straddled a harvest period rather than a specific harvest date, e.g., residues from 15 to 60 days after application versus exactly 30 days after application for mature citrus fruits.

Should the pre- and post-tolerance-assignment residue data differ markedly - without changes in formulations, dosages, numbers of applications, or timing - the major causes to be suspect are changes in the residue analytical methodology or in the adequacy of the sampling for either the initial or the monitoring program. In general, residue analytical methodology is steadily improving in both quality and quantitative reliability and more incisive data would be expected today than were achievable 10 to 20 years ago, especially in terms of prob­able metabolites included in the "apparent" residue value; on the other hand, developmental residue data are usually obtained from extrava­gantly large field samples and number of replicates to represent the crop in the field, whereas monitoring and other quality-assurance data are often from statistically meager samples taken somewhere between field and consumer, often at the end of the packing house line with citrus fruits. In some important instances, earlier and current analytical procedures can be compared for reliability, but it is not easily possible to correlate a field sampling program with the usual market sampling program; the former presumably establishes a range of values en­compassing the mean or average residue load from the field applica­tion, whereas the latter ideally should demonstrate the maximum residue present in a shipment, a carload, a lot,a carton, etc. Some guidelines for field-sampling programs have been adequately estab­lished for various crops; how to sample in a postharvest residue sur­veillance or monitoring program is still a matter of empirical judgment influenced in part by the time available to the sampler, but mostly by the economics of purchasing the samples, the nature and size of the crop unit on the market, the size of the lot involved, sample storage space available to the residue laboratory, the grinding and extraction equipment available in the laboratory, and others. Over a long enough period, the continuing "market-basket survey" initiated by the U.S. Food and Drug Administration is undoubtedly the most realistic ap­proach to this problem. As has been shown (DE Vos 1968), taking half a dozen fruits from a carton or market display is not a realistic answer

4 Examining in a suspect area or situation, usually in the field but often in the wholesale market; guided samples.

II Examining at random, usually with market or wholesale samples; random samples.

Insecticide residues in citrus fruits 5

to the problem of sampling citrus fruits on the market, even for the in-carton applied citrus fungistat biphenyl. Sampling a carton of citrus fruits to establish a reliable mean and a maximum residue load is not a simple matter: with insecticides, fruits in a given carton could be from different areas and even have different insecticides in the rind tissues, for example [see section X b)].

The present report therefore attempts to collate and summarize the data available for insecticide and acaricide residues on and in Cali­fornia citrus fruits 6 as established (for the chemicals included) for licensing, registration, and tolerance classification at both the state and the federal levels. Also presented and discussed are the few data avail­able for the citrus products dried citrus pulp cattle feed, expressed juice, cold-pressed oil, and dried orange rind. Some of these residue data on both fresh fruits and products have not previously been published nor have they previously been collected and compared as in the present review. Included for comparisons are some "market" residue data re­cently accumulated in a quality assurance program of the members of the California-Arizona Citrus Industry, to whom appreciation is ex­pressed for permission to incorporate their findings in the present report.

A little of the published information on pesticide residues in citrus fruits has been briefly reviewed by STOBWASSER et al. (1968) in their extensive review of postharvest factors and pesticide residues in crops and crop products.

As developed in the present review, some of the compounds herein included are no longer used in California-Arizona citriculture, or dos­ages and methods of application have been changed since the original residue data were developed. Some of the present developmental data are therefore not strictly representative of present field recommenda­tions and practices, but are included for the sake of completeness. Every effort has been made to point out these disparities in text and in legends to figures and in footnotes to tables. Throughout the text are also incorporated other details to make this review as seHsufficient as reasonably possible for the benefit of the reader unfamiliar with certain background information basic to this particular series of domestic in­secticide residue investigations, such as the verbatim incorporation of residue-analytically important sections of the definitive U.S. Public Law 83-518, generalized explanations of pesticide residue "behavior," and the present two, broad, information-seeking market survey pro­grams for insecticide residues in marketed citrus fruits. Because they

6 Mostly Eureka lemons, Valencia oranges, and Washington navel oranges; occasional data for Marsh grapefruit are included, although residue behavior on grapefruit, tangerines, and most other citrus varieties is considered to be bracketed by the residue behavior of the same dosage of the same formulation on lemons and oranges. Occasionally, supporting residue data for some of these other varieties have been required.

6 F. A. GUNTHER

have never before been published in sufficient detail, laboratory pro­cedures for the analytical storage, processing, and treahnent of ex­tractives from citrus fruits are included, along with the laboratory­scale preparation of dried citrus pulp cattle feed, a major feed item of the dairy industry. The advantages and disadvantages of the com­monly used residue-extracting solvents are discussed for the present application.

II. Residue legislation

Since the major part of the California citrus crop enters interstate commerce it is predominantly subject to federal regulation in regard to residue contents from insecticides applied before harvest. California reSidue-regulating legislation closely conforms to that of the federal government with reference to citrus fruits, however.

As public health agencies in the United States realized in the very early 1950's, residues-in-foodstuffs data should constitute requirements preceding the legalized, commercial use of any pesticide, as formally expressed in 1954 in U.S. Public Law 83-518, or Miller Bill, or Pes­ticide Chemicals Amendment. This law resulted in the present-day "tolerance" concept and the establishment by experts of safe and legal (permitted) amounts of residues in foodstuffs and feeds. Both the general concept and the practice of residue tolerance requirements are being accepted and promoted by governments around the world. Pub­lic Law 83-518 (specifically, Section 408 of the Federal Food, Drug, and Cosmetic Act) defines a pesticide chemical as "any substance which alone, in chemical combination or in formulation with one or more other substances, is an 'economic poison' within the meaning of the 1947 Federal Insecticide, Fungicide, and Rodenticide Act (7 U.S.C. secs. 135-135k) as now in force or as hereafter amended, and which is used in the production, storage, or transportation of raw agricultural commodities." The latter act defines an economic poison (and hence a pesticide chemical) as "( 1) any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any insects, rodents, nematodes, fungi, weeds, and other forms of plant or animal life or viruses, except viruses on or in living man or other animals, which the Secretary shall declare to be a pest, and (2) any substance or mixture of substances intended for use as a plant regula­tQr, defoliant or desiccant." Also from Public Law 83-518, "raw agricul­tural commodity" is defined as "any food in its raw or natural state, including all fruits that are washed, colored, or otherwise treated in their unpeeled natural form prior to marketing." Thus, whole citrus fruits up to the point of marketing are considered still to be raw agricultural commodities.

The Food Additives Amendment of 1958 (Public Law 85-929) to

Insecticide residues in citrus fruits 7

the Federal Food, Drug, and Cosmetic Act states that the term "food additive" does not include "a pesticide chemical in or on a raw agricultural commodity" or "a pesticide chemical to the extent that it is intended for use or is used in the production, storage, or transporta­tion of any raw agricultural commodity."

TIl. Tolerances

a) Establishment of tolerances

By enactment of Public Law 83-518, the 83rd Congress of the United States also amended the Federal Food, Drug, and Cosmetic Act by adding a new section on tolerances 7 for pesticide chemicals in or on raw agricultural commodities:

"Sec. 408. (a) Any poisonous or deleterious pesticide chemical, or any pes­ticide chemical which is not generally recognized, among experts qualified by scientific training and experience to evaluate the safety of pesticide chemicals, as safe for use, added to a raw agricultural commodity, shall be deemed unsafe for the purposes of the application of clause (2) of section 402 (a) unless-

"( 1) a tolerance for such pesticide chemical in or on the raw agricultural commodity has been prescribed by the Secretary of Health, Education, and Wel­fare under this section and the quantity of such pesticide chemical in or on the raw agricultural commodity is within the limits of the tolerance so prescribed; or

"(2) with respect to use in or on such raw agricultural commodity, the pesticide chemical has been exempted from the requirement of a tolerance by the Secretary under this section. "While a tolerance or exemption from tolerance is in effect for a pesticide chemical with respect to any raw agricultural commodity, such raw agricultural commodity shall not, by reason of bearing or containing any added amount of such pesticide chemical, be considered to be adulterated within the meaning of clause (1) of section 402 (a).

"(b) The Secretary shall promulgate regulations establishing tolerances with respect to the use in or on raw agricultural commodities of poisonous or deleterious pesticide chemicals and of pesticide chemicals which are not generally recognized, among experts qualified by scientific training and experience to evaluate the safety of pesticide chemicals, as safe for use, to the extent necessary to protect the public health. In establishing any such regulation, the Secretary shall give appropriate consideration, among other relevant factors, (1) to the necessity for the production of an adequate, wholesome, and economical food supply; (2) to the other ways in which the consumer may be affected by the same pesticide chemical or by other related substances that are poisonous or deleterious; and (3) to the opinion of the Secretary of Agriculture as submitted with a certification of usefulness under sub­section (1) of this section. Such regulations shall be promulgated in the manner

7 A tolerance in this connotation is the amount of residue legally permitted to remain on or in the commodity and is usually expressed as parts per million (p.p.m.) or milligrams of pesticide per kilogram (mg./kg.) of foodstuff.

8 F.A.GUNTHER

prescribed in subsection (d) or (e) of this section. In carrying out the provisions of this section relating to the establishment of tolerances, the Secretary may estab­lish the tolerance applicable with respect to the use of any pesticide chemical in or on any raw agricultural commodity at zero level if the scientific data before the Secretary does not justify the establishment of a greater tolerance.

"( c) The Secretary shall promulgate regulations exempting any pesticide chemical from the necessity of a tolerance with respect to use in or on any or all raw agricultural commodities when such a tolerance is not necessary to protect the public health. Such regulations shall be promulgated in the manner prescribed in subsection (d) or (e) of this section.

"( d) (1) Any person who has registered, or who has submitted an applica­tion for the registration of, an economic poison under the Federal Insecticide, Fungicide, and Rodenticide Act may file with the Secretary of Health, Education, and Welfare, a petition proposing the issuance of a regulation establishing a tolerance for a pesticide chemical which constitutes, or is an ingredient of such economic poison, or exempting the pesticide chemical from the requirement of a tolerance. The petition shall contain data showing -

"(A) the name, chemical identity, and composition of the pesticide chemical;

"( B) the amount, frequency, and time of application of the pesticide chemical;

"( C) full reports of investigations made with respect to the safety of the pesticide chemical;

"( D) the results of tests on the amount of residue remaining, including a description of the analytical methods used;

"( E) practicable methods for removing residue which exceeds any pro­posed tolerance;

"( F) proposed tolerances for the pesticide chemical if tolerances are proposed; and

"( G) reasonable grounds in support of the petition. "Samples of the pesticide chemical shall be furnished to the Secretary upon re­quest. Notice of the filing of such petition shall be published in general terms by the Secretary within thirty days after filing. Such notice shall include the analytical methods available for the determination of the residue of the pesticide chemical for which a tolerance or exemption is proposed.

"( 2) Within ninety days after a certification of usefulness by the Secretary of Agriculture under subsection (1) with respect to the pesticide chemical named in the petition, the Secretary of Health, Education, and Welfare shall, after giving due consideration to the data submitted in the petition or otherwise before him, by order make public a regulation -

"( A) establishing a tolerance for the pesticide chemical named in the petition for the purposes for which it is so certified as useful, or

"( B) exempting the pesticide chemical from the necessity of a tolerance for such purposes,

"unless within such ninety-day period the person filing the petition requests that the petition be referred to an advisory committee or the Secretary within such period otherwise deems such referral necessary, in either of which events the provisions of paragraph (3) of this subsection shall apply in lieu hereof.

"( 3) In the event that the person filing the petition requests, within ninety days after a certification of usefulness by the Secretary of Agriculture under sub-

Insecticide residues in citrus fruits 9

section (1), with respect to the pesticide chemical named in the petition, that the petition be referred to an advisory committee, or in the event the Secretary of Health, Education, and Welfare within such period otherwise deems such referral necessary, the Secretary of Health, Education, and Welfare shall forthwith submit the petition and other data before him to an advisory committee to be appointed in accordance with subsection (g) of this section. As soon as practicable after such referral, but not later than sixty days thereafter, unless extended as hereinafter provided, the committee shall, after independent study of the data submitted to it by the Secretary and other data before it, certify to the Secretary a report and recommendations on the proposal in the petition to the Secretary, together with all underlying data and a statement of the reasons or basis for the recommenda­tions. The sixty-day period provided for herein may be extended by the advisory committee for an additional thirty days if the advisory committee deems this necessary. Within thirty days after such certification, the Secretary shall, after giving due consideration to all data then before him, including such report, recom­mendations, underlying data, and statement, by order make public a regulation -

"(A) establishing a tolerance for the pesticide chemical named in the petition for the purposes for which it is so certified as useful; or

"( B) exempting the pesticide chemical from the necessity of a tolerance for such purposes. "( 4) The regulations published under paragraph (2) or (3) of this subsec­

tion will be effective upon publication."

Section (d) ( 1) above specifies that the petition for tolerance classification shall include data showing "the results of tests on the amount of residue remaining, including a description of the analytical methods used" as well as "practicable methods for removing residue which exceeds any proposed tolerance." As will be shown later (Table XVII), a few insecticides penetrate citrus rind so slowly that normal packing house washing procedures markedly diminish the residue load, but washing has little effect on many aged residues on and in citrus fruits.

Presentations of residue data to the U.S. Food and Drug Admin­istration for tolerance assignment and to the U.S. Department of Agri­culture (HARRIS and CUMMINGS 1964) must (subsection D above) include a sufficiently detailed description of the analytical method ( s) used that residue chemists of both agencies can if desired reproduce and evaluate the adequacy of the proposed method in its intended purpose and in application to the raw agricultural commodities in­volved in the petition.

b) Pertinent insecticide tolerances for citrus fruits

Several other countries have established tolerances for pesticide residues in foodstuffs (GUNTHER 1966 and 1968 a and b) and numerous countries have either comprehensive revisions (updating) of old legis­lation or completely new legislation under consideration. Examples of the former are Canada, Italy, The Netherlands, West Germany, and

10 F.A.G'ONTHER

Table I. Present tolerances for insecticides and acaricides on and in citrus fruns (quoted in HAZLETON 1968, ANONYMOUS 1968 b for Italy)

Tolerance (p.p.m.)

Insecticide The Neth- West Proposed United Canada Italy erlands Germany EEC States

Key materials (over fruit)

Bidrin - - - - - 0.25 Carbaryl 2.0 a 3.0 3.0 3.0 3.0 10 Chlordane 0.3 0.2P 0.1 Prohibited 0.2 II 0.3 Chloro-

benzilate 8.0 - 2.0 - 1.5 5.0 DDT 7.0 1.0 1.0 1.0 a 1.0 7.0 0

Dicofol 3.0 a - 2.0 0.5 - 10 Dioxathion 2.5 - 1.0 0.4 - 2.8 Malathion 4.0&8.0 a 3.0 3.0 0.5 0.5 8.0 Methyl

parathion 1.0 a 1.0 0.5 0.5 0.5 1.0 Parathion 1.0 a 0.5 0.5 0.5 0.5 1.0 Petroleum

oils Safe - - - - Exempt Rotenone Safe - - 0.04 - Exempt TDE(DDD) 7.0 - - - - 7.0 Toxaphene 7.0 - 0.4 0.4 a 0.4 7.0

Highly useful materials (over fruit)

Azinphos methyl -<I 0.4 0.5 0.4 0.4 2.0

Mevinphos 0.25 a - 0.5 0.1 - 0.25 Naled - - - 0.2 - 3.0 Sabadilla Safe - - - - Exempt Sulfur Safe - - 50 - Safe

Highly useful materials (nonbearing)

Aramite Prohibited - - Prohibited Zero Zero Dimethoate 2.0&4.0 a 0.6 0.5 0.5 0.6 -Heptachlor 0.1 a 0.2 P 0.1 Prohibited 0.111 Zero d

Neotran - - - - - Zero d

Phos-phamidon - 0.5 - 0.1 & 0.5 II 0.5 1.0 e

Nonessential

Carbo-phenothion o.sa - - - - 2.0

Demeton 0.5 0.4 - 0.4 0.4 0.75 Diazinon 0.75 - 0.5 0.5 - 0.75 Dieldrin 0.1 &0.25 a 0.2P 0.1 Prohibited 0.2 II 0.05 E thion 2.0 - 0.5 - - 2.0

a Tolerance not for citrus fruits. b EEC proposes a tolerance for aldrin, chlordane, dieldrin, heptachlor, and

heptachlor epoxide of 0.2 p.p.m. individually or combined until 31 December 1972 and a zero tolerance for each after 1 January 1973.

C Jointly proposed (19 February 1968) by the U.S. Food and Drug Admin­istration and the U.S. Department of Agriculture to be reduced to 3.5 p.p.m. on 12 crops and 1 p.p.m. for 24 crops for 1968, with all DDT tolerances at 1.0 p.p.m. beginning with the 1969 growing season (ANONYMOUS 1968 a).

rl Nonfood use, except for 0.1 p.p.m. of heptachlor on a few crops (not citrus fruits) .

e Petition pending. I Depending upon compound: 1.0 p.p.m. for the dicyclohexylamine salt of

dinitro-o-cyclohexylphenol, but nonfood use only for DNBP (a dinitrobutyl phenol).

g Aldrin, chlordane, dieldrin, heptachlor, and heptachlor epoxide are 0.2 p.p.m. individually or combined.

the U.S.S.R.; examples of the latter are France, Japan, Spain, and many others. Just as United States' tolerances have affected the local production and marketing of citrus crops, other-country tolerances will affect exports of citrus fruits and products, especially if the "foreign" tolerances are lower than ours. In the event of lower tolerances abroad and the wish to continue exports, it is highly likely that production

12 F. A. GUNTHER

pest-control practices will have to be altered, for our tolerances gener­ally reflect the maximal but still safe amounts of residues that could be present from necessary and good agricultural practices. In addition, the European Economic Community (EEC) has just released toler­ances for 19 pesticides, some of which are currently used in citrus pest control, and a longer supplementary list is to be issued in early 1969; presumably, most of these tolerances will be adopted by most of the member countries. Also, WHO/FAO through various commissions and the Codex alimentarius are similarly influencing tolerance assignments for specmc major pesticides on and in specific major foodstuffs. Pro­ducers of crops must, therefore, meet both domestic and foreign toler­ance requirements if their products are to be accepted in international trade.

In Table I are listed the major insecticides and acaricides currently important to the culture of citrus fruits, with the applicable tolerances of Canada, Italy, The· Netherlands, West Germany, proposed EEC, and the United States. The in-table categories of usefulness are based largely upon current California recommendations for citrus pest con­trol. In addition, Japan has just established some tolerances, but citrus fruits are not yet included among the substrates specmed (lsIUI 1968); it is to be expected that supplemental lists for other pesticides and additional crops and crop products will follow. Insecticides and crops presently included in the Japanese listing are shown in Table I1a. The

Table IIa. Japanese tolerances for insecticide residues (ISHII 1968)

Insecticide and tolerance (p.p.m.) a

Crop I Arsenic I Lead 'Y-BHC DDT Parathion (as As.O.) (as Pb)

Apples 0.5 1.0 0.3 3.5 5.0 Grapes 0.5 0.5 0.3 1.0 1.0 Cucumbers 0.5 0.5 0.3 1.0 1.0 Tomatoes 0.5 0.5 0.3 1.0 1.0

a Effective 1 October 1968.

Japanese tolerance for parathion, widely used in citriculture, is con­sistently 0.3 p.p.m., whereas the other countries included in Table I established either 0.5 or 1.0 p.p.m. for this important insecticide. Similarly, except for apples, the Japanese tolerance for DDT is lower than the other adoptions. Some pertinent U.S.S.R. tolerances are shown in Table lIb.

Insecticide residues in citrus fruits

Table lIb. U.S.S.R. tolerances a for insecticide residues ( MELNIKOV 1968)

Insecticide

Aldrin Chlordane DDT Dieldrin Heptachlor Malathion Mercury compounds Methyl parathion Parathion

Tolerance (p.p.m.) a

Zero Zero 0.5 b

Zero Zero

8 Zero 1.0· 1.0·

a Zero for all organochlorine compounds on and in meat, milk, and grain. b On and in all fruits. C Including metabolites.

13

For citrus fruits, the established tolerances that apply are in­terpreted on an "as is" basis; that is, the p.p.m. value is based upon the amount of insecticide in the whole fruit as it would be purchased on the market and, therefore, reflects the mg. of insecticide/kg. of whole fruit including rind, pulp (juice plus rag), and seeds. Specific toler­ances for citrus products such as dried citrus pulp cattle feed,S oil of lemon and oil of orange, frozen juice, etc., have not been generally established in the United States. Tolerance equivalents for these products (if needed) are apparently extrapolated from a whole fruit baSiS, with fresh whole juice representing from about ~ to about ~ of the weight of the whole fruit, recoverable cold-pressed oil from 0.1 to 0.8 percent, and dried citrus pulp cattle feed from about J4 to about ~ of the weight of the whole fruit with an eventual desiccation factor of about eight, or from about 85 percent moisture (total volatiles) to about 10 percent moisture (total remaining volatiles) (see also Fig. 27). In Table III are listed proportions of rind and oil in some whole California citrus fruits as guides. These figures are to be used as guides only because of recognized wide variations in rind thickness and density with climate, rootstock, vigor of tree, fertilizer program, and many other factors (see Table III, footnote a).

S With most pesticides used in citriculture, however, residue data for the dried citrus pulp cattle feed are asked for as part of the petition. Consequently, prepara­tion and residue analysis of this product should be a part of every citrus fruit residue program. To date, established, specific tolerances for insecticide residues in this product are carbophenothion 10 p.p.m., dioxathion 18 p.p.m., ethion and its oxygen analog 10 p.p.m., azinphos methyl five p.p.m., and malathion 50 p.p.m.

14 F. A. GUNTHER

Table m. Proportions of rind and oil in whole California cit1'U8 fruits

Source

Mature fruit GUNTHER ( 1950) Sunkist Growers, Inc. a

No. of Rind II (%) measurements Rind (%) Oil (%)

Grapefruit 23.0 ± 3.2 47 ca. 50 ca. 0.6 Lemons 30.0 ±8.5 632 25 0 -40" ca. 0.8 Navel oranges 22.1 ± 7.3 567 50 ca. 0.6 Valencia oranges 18.7 ± 6.3 297 40 ca. 0.8

a Maximum amounts (by steam distillation) from commercial processing plant data (SWISHER 1968), where "rind" also includes rag. Total "extractable" oils range from about 0.1 to about 0.8 percent on a mature, whole-fruit basis. The amount of cold-pressed oil commercially recoverable by mechanical extraction methods is less and depends on such major factors as maturity of the fruit and the type of equipment used. SINCLAIR (1961) reports on the other factors which also affect the yields of rind oil. See also Figure 27 for oil recovery data from the schematically presented processing operations in products manufacture.

II Includes both albedo and flavedo. o Storage. " Fresh and turgid.

IV. Generalized insecticide residue behavior on and in citrus fruits

Deposits and residues of the inorganic citrus insecticides such as the lead and calcium arsenates, lime-sulfur, cryolite, etc. adhered to and remained on the surfaces of the rinds of citrus fruits. They were thus easily removed or at least greatly diminished by the usual packing house washing and brushing operations. This behavior was also true of those DN compounds used as salts, but in retrospect it was not true for rotenone, sabadilla, free nicotine, and the other organic materials commonly used before DDT was developed. It was not realized at the time that these chemicals actually penetrated in part into subsurface regions of the sprayed or dusted fruits. This realization came after attempts had been made to evaluate DDT as nonpenetrating deposits on citrus fruits, and was soon strikingly confirmed with the more rapidly penetrating parathion, again on citrus fruits.

Deposits and residues of any of these chemicals are not synony­mous terms. The word "deposit" refers to the chemical as initially laid down on the plant sudace by the treatment, whereas the word "residue" refers to the chemical regardless of locale on or within the plant part and with the implication of aging by time lapse or altera-

Insecticide residues in citrus fruits 15

tion, or both (GUNTHER 1962 and 1966). It follows that a deposit becomes a residue as soon as it is affected by weathering, metabolic conversions, or other processes that cause alteration, degradation, com­plex formation, or migration. The distinctions among the successive stages of initial deposit, effective deposit, effective residue, and pene­trated residue are tenuous at best, and the hours or days required to shift from one stage to the next will vary with the chemical and physical properties of the pesticide as the major factors.

Magnitudes of initial deposits are also influenced by many factors including nature and dosage of chemical, composition of formulation, method and uniformity of application, varietal differences among the trees, environmental differences, seasonal differences, and others. Initial deposits normally consist of piled layers of loosely bound material, with only the bottom layer tightly bound to the plant surface by the adhesive properties of the formulation and the physical and chemical structure of the plant surface.

a) Degradation and persistence curves

As soon as deposited material not adhering tenaciously to the fruit (or leaf) surface sloughs off, the remaining portion of the initial de­posit becomes the stabilized portion of an effective 9 depOSit, then an effective residue as it begins to penetrate the rind, then a penetrated residue by extensive migration into (and perhaps through 10) the rind, as illustrated schematically in Figure 1: X represents physically dis-

ror-----------------~

5

10 20

Days after application

Fig. 1. Graphical demonstration of idealized insecticide residue behavior on and in citrus fruit rind (see text for explanation and references)

9 Effective in terms of biological effectiveness, i.e., availability to chewing, rasping, and/or sucking insects or by contact absorption.

10 For example, with a systemic insecticide.

16 F.A.Gt1NTHER

placed compound as by sloughing or other dislodgment of the upper loosely bonded layers of the initial deposit, Y represents a typical degradation curve from the combined actions of sloughing, codistilla­tion with plant respirants, volatilization, photodecomposition, hydrol­ysis, oxidation, and penetration,l1 and Z represents a typical persist­ence curve of the penetrated material which is now subject only to metabolic and hydrolytic attack plus (sometimes) the reissuance or redistribq.tion phenomenon (GUNTHER et al. 1946, GUNTHER and BLINN 1955). Such idealized curves obviously represent summations of these and perhaps other processes going on simultaneously with actual gradual transitions from one slope to the next.

Since citrus fruits have essentially discontinuous wax surfaces, favorably soluble compounds can surprisingly quickly dissolve in the waxy and oily components of the rind, where they may reside un­changed for long periods. Both systemic and nonsystemic chemicals can penetrate into citrus rind, however, through both the aqueous and the nonaqueous pathways always present (CRAFl'S and Foy 1962, EBELING 1963, LINSKENS et al. 1965). It is of interest to note that some systemic pesticides are transported within plant tissues at rates up to 100 cm./hr. (HULL 1960); the systemic insecticide demeton was found to move in citrus tissues at about 10 cm./hr. (WEDDING 1953).

From these considerations it is clear that slowly penetrating resi­dues can be removed readily and probably nearly quantitatively from mature citrus fruits by washing and brushing (see Table XVII), for such removal would require only the simple cleaving of any mechan­ical bond between deposit, effective deposit, or effective residue and the fruit cuticle formed largely as the result of adhesives or wax solu­bilizers in the formulation.

Penetrating and degrading residues (Y in Fig. 1) tend to disappear or degrade at rates, for each chemical and each variety, which are approximately direct functions of the applied concentrations of the parent chemicals (GUNTHER and BLINN 1955, GUNTIIER 1962); the percentage or fractional decreases of residues with time, however, are independent both of initial concentration and of magnitude of deposit. Similarly, the persisting penetrated residues (Z in Fig. 1) also dis­appear or are degraded at a constant but slower rate for each chemical and sometimes for each variety. With most plant tissues these pro­cesses of degradation and persistence generally follow the pathway resultant from first-order reaction kinetics (GUNTHER and BLINN 1955, HOSKINS 1961, FREAR 1963, COOK 1965), as especially noteworthy with nonsystemic insecticides in citrus rind. Thus, these variously called

11 The question of the fate of the disappearing portion of the deposit or aging residue was first raised with evaluations of residues of DDT on and in citrus fruit rind and foliage (GUNTHER 1945 and 1946, GUNTHER and BLINN 1956).

Insecticide residues in citrus fruits 17

degradation, persistence,l2 disappearance, time-decay, or attenuation curves for a specific compound may be plotted semilogarithmically as straight lines of log residue, log p.p.m., or fraction of residue loss or retention against time elapsed since treatment, as shown earlier in Figure 1 and in practical detail in Figure 2. Time-decay values for leaf

E ci. ci.

l00~------~---------r--------'---------'

20 40 60 80 Days after application

Fig. 2. Idealized and illustrative degradation and persistence curves for nonsys­temic insecticides on and in Valencia orange leaf and rind tissues (mala­thion dosage: three lb. 25 percent wettable powder/100 gallons, 1,500 gallons/acre) (GUNTHER and WESTLAKE 1968)

deposits and residues normally follow rather closely a gentle, sym­metrically curved line when p.p.m. or p.g./cm.2 are plotted directly against elapsed days (GUNTHER 1946, GUNTHER et al. 1946), but a straight line (curve A) when plotted on semilog paper. Aging rind residues, on the other hand, generally exhibit a nonsymmetrical curvil­inear behavior on an arithmetic basis (see lower dashed curve) and two intersecting straight lines (curves Band C) on a semilog basis. These two types of plots are illustrated with actual malathion data in this figure. Curve B is the degradation curve and curve C is the per­sistence curve (GUNTHER and BLINN 1955). Curve B represents dis-

12 The originally proposed "persistence" curve is being displaced by "time­decay curve," "dissipation curve," or "disappearance curve" because of the some­times undesirable connotation of the word "persistence."

18

Fig. 3

Fig. 4

>. .s:: ... QI E .. o

.s:: Q.

.!: N «

30

1.0

~ 0.1 ci

.! 'f 20.0 <

F.A.GUNTHER

Whole·fruit basis

Days

-~---------l___ 1 I -----+_ Valencia oranges

Insecticide residues in citrus fruits 19

Fig. 3. Degradation and persistence curves of Aramite on and in Eureka lemons. whole-fruit basis; dosage: 0.3 lb. actual (15 percent wettable powder)/loo gallons, 1,500 gallons/acre (no longer used on bearing trees in California­Arizona citriculture) [GUNTHER and JEPPSON, Unpublished (1950) and GUNTHER et al. 1951]. See also Figure 30

Fig. 4. Persistence curves of azinphos methyl on and in Eureka lemon and Valen­cia orange rinds (see Table III); dosages: one lb. actual (25 percent wettable powder)/100 gallons, 1,500 gallons/acre for lemons, 2,500 gal­lons/ acre for oranges (GUNTHER et al. 1963). The original publication also includes residue persistence data for one-fourth the above dosage as well as the effects of rainfall on deposits and residues of this insecticide on and in both citrus varieties

Fig. 5

10

5.

~ 1.0 0." ci.

"~ .t; iii 0.5

Days

Fig. 5. Degradation and persistence curves for Bidrin on and in Valencia orange rind (see Table III); dosage: 1.4 lb. actual (technical grade compound)/ 100 gallons, 2,500 gallons/acre (MURPHY et al. 1965 a and b). The latter publication also includes residue persistence data for 0.5 and 1.0 lb. actual (technical grade compound) /100 gallon dosages

20

Fig. 6

Fig. 7

F. A. GtJNTHER

30

10

E ci ci

>. 5 ... C

-'l ... C

U Eureka lemons

10L--~----4~0--~--~6~0~~--~1~20'-~ Days

30

l 20 \.

\l S

''1. I \\ Eureka lemons

C2HsO, , 0-C2 HSO /P-S-CH2-S ~ CI

8 c: .2 6 ..c: .. o c: 1 4

Q. o

-'l ... o

U

2

............... ,............. Total chloride ............. /

... 1 ......................... 1 .. ...... .

10 20 30 40 Days

70

Insecticide residues in citrus fruits 21

Fig. 6. Degradation and persistence curves for carbaryl on and in Eureka lemon and Valencia orange rind (see Table III); dosage: one lb. actual (50 per­cent wettable powder)/loo gallons, 1,500 gallons/acre (GUN'I1IER sf al. 1962 a). The original publication also includes residue persistence data for two lb. actual (50 percent wettable powder)/loo gallons

Fig. 7. Degradation and persistence curves for carbophenothion on and in Eureka lemon rind (see Table III); dosage: 0.6 lb. actual (37 percent emulsive concentrate)/loo gallons, 1,500 gallons/acre (GUN'I1IER et al. 1959). The original publication also includes residue persistence data for navel oranges. Several dosages (0.25,0.75, and 1.5 lb. actual/loo gallons) of a 25 percent wettable powder formulation were also evaluated for both varieties by two analytical methods

Fig. 8 50

CI CI$jCI ij H

CI-C-CI H

CI H CI

CI H H

10~--~ro~--~20~--~~~~~

Days

Fig. 8. Degradation and persistence curves for chlordane on and in Eureka lemon rind (see Table III); dosage: two lb. actual (50 percent wettable pow­der)/loo gallons, 200 gallons/acre (skirt and trunk applications only) [GUN'I'HER and CuoouN, Unpublished (1955), BLINN sf al. 1959 a]

22

Fig. 9

7 ci. ci.

• .. ,g ... c: .,

..a o .. o :c u 2

F.A.GUNTHER

COOC2"S

CIO~OCI Eureka lemens OH

lL---~----~----~--~----~----~--~ o

Fig. 10

20

6.0

60 Days

CI{) ~ CI '/C-&-CI CI-Q b,

Valenoia CII'/1IIges

Whole-fruit basis

100

0.10!:--1-~20~-1--4b;O--l..--;6~O-...I

Days

140

Insecticide residues in citrus fruits 23

Fig. 9. Persistence curves of chlorobenzilate on and in Eureka lemon rind (see Table III); dosage: four oz. actual (25 percent wettable powder)/100 gallons, 1,000 gallons/acre (BLINN et al. 1954, GUNTHER et al. 1955). The latter publication also includes residue persistence data by both chemical and biological assays for the above and 12 oz. dosagss; the former publica­tion also includes solubility data for chlorobenzilate in five organic solvents

Fig. 10. Degradation and persistence curves for DDT on and in Valencia oranges, whole-fruit basis; dosage: two lb. actual (50 percent wettable powder) / 100 gallons, 250 gallons/acre (ATKINS et al. 1961). The original publica­tion also includes residue persistence data from both one/fourth and one­half the above dosage

Fig. 11

Ii Ii Ii

c o c .;:;

" is 0.5

Valeneia Of"anl"

Days

Fig. 11. Degradation and persistence curves for diazinon on and in Eureka lemon and Valencia orange rind (see Table III); dosage: 0.5 lb. actual (25 peroent emulsive concentrate)/I00 gallons, 1,500 gallons/acre (not yet a recommended material in California-Arizona citriculture) (GUNTHER et al. 1958 a). The original publication also includes residue persistence data and curves for the same dosage of a 25 percent wettable powder/ 100 gallons; the results of triangular Havor tests on the juices from some of these treated fruits are also tabulated and discussed

24

E ci ci

'0 -o u o

Fig. 13

F. A. GUNTHER

s........ Ketone method "... lJ ............ !?...... / 0 Total chloride method

- ... oA, ........... / -----4.. I ................. . • -..,,--"-!r----~-:;-~-:::::::::.= .. ~ ... ~ ....... . ----A___ 0 .................. .

----E-------.. ChlorofCR711 method

Valencia oranges

2

lL----L----~--~-----L----~--~----~ o 20

c I;: "V .. o

40 P \ Eureka 1emona

\ , \ ,

\ T ._,- . ... -:.,L. ......

Days

.... ...... r • ...

... .... .... .. .. '1:

~~~~~1~O--~--~2~0--~--~30~~

Days

Insecticide residues in citrus fruits 25

Fig. 12. Persistence curves for dicofol on and in Valencia orange rind (see Table III); dosage: 0.4 lb. actual (25 percent wettable powder)/100 gallons, 1,500 gallons/acre [GUNTHER and JEPPSON, Unpublished (1956), GUN­

THER et al. 1957]. The original publication includes similar data for Eureka lemons and, for both varieties, the complete persistence curves for an emulsive concentrate formulation; some of the curves are based upon multiple residue analytical methods. GUNTHER and BLINN (1957) report partition ratios of dicofol between petroleum ether and acetonitrile and hydrolysis rate constants of dicofol in ammonia-ethyl alcohol solutions

Fig. 13. Degradation and persistence curves for dieldrin on and in Eureka lemon and Valencia orange rind (see Table III); dosage: one lb. actual (50 percent wettable powder) 1100 gallons, 1,500 gallons I acre (GuNTHER et al. 1954, BLINN et al. 1959). The former publication also includes harvest residues on and in both immature and mature navel oranges from several dosages and formulations. See also Figure 29

Fig. 14

E ci. ci.

Q) .... o o

..s::. .... Q)

E C\

20

8

6

4

2

\ \

~1 CH30, .... S

CH30./ P ' SCH2 CONHCH3

.Il , Valencia oranges ':yo

'i .. l ".J. T 'r", T

I .. "'" I .. f .L ....

• ...,T", 1 .. .0 lb. dosage

~ ...... T .L ........ q

1".. ... .. , "', h

.... I. ........

o~ __ ~ __ ~~ __ ~ __ ~~ __ ~ __ __ o 10 20 30 40 50

Days

Fig. 14. Degradation and persistence curves for dimethoate on and in Valencia orange rind (see Table III); dosages 0.5 and 1.0 lb. actual (50 percent emulsive concentrate) 1100 gallons, 2,500 gallons/acre (GUNTHER et al. 1965). The original publication also includes residue persistence data from two field applications of these dosages 18 days apart

26

Fig. 15

Fig. 16

Ii d d

g 1 :c. ... o " o

i5 o.

F.A.GUNTHER

Navel oranges

O.lO~ --L._-..I.40---JL---Sl..O---L--l..l20--

.... E Ii Ii

c 5 o :c

+0-w

Doys

Eureka lemons

Insecticide residues in citrus fruits 27

Fig. 15. Degradation and persistence curves for dioxathion on and in Eureka lemon and navel orange rind (see Table III); dosage: six oz. actual (25 percent wettable powder) / 100 gallons, 2,500 gallons/acre (GUNTHER et al. 1958 b). The original publication also includes residue persistence data for 6, 12, 24, and 48 oz. of an emulsive concentrate (four Ib./ gal-10n)/100 gallons on both varieties

Fig. 16. Degradation and persistence curves for ethion on and in Eureka lemon and Valencia orange rind (see Table III); dosages: one lb. actual (25 percent wettable powder )/100 gallons, 1,500 gallons/acre for lemons, 2,500 gallons/acre for oranges (GUNTHER et al. 1962 b). The original publication also includes residue persistence data for four oz. actual (25 percent wettable powder )/100 gallons and for one-fourth pint (87 per­cent emulsive concentrate)/100 gallons dosages for both varieties and for a 2.6 percent formulation in oil on the oranges; partition ratios for ethion between n-hexane and acetonitrile are also reported

Fig. 17

Fig.

E Ii Ii .. ~ ..c u .E Q. Q)

J:

10

0.5

Cl

CI$b CI-C-CI H

CI H H CI H CI

O. 10tl-"----;2!::O--L.--::41::-0--L--:!6l::-0-..J

Days

17. Degradation and persistence curves for two formulations of heptachlor on and in Eureka lemon rind (see Table III); dosages: two lb. actual (30 percent wettable powder or 20 percent emulsive concentrate)/loo gal­lons, 350 gallons/acre [GUNTHER and CARMAN, Unpublished (1954), BLINN et al. 1959]

28

Fig. 18

Fig. 19

5.0

1 ~ 1.0

c o :c .. ~ o. ~

0.1 0

10

9

7

6

5

E 4 ci ci

c

~ 3

• ~

:E

2

F.A.GUNTHER

CH30 ...... s CH3 a '" p ... s - CH - COOCz H5

I

I CHz-COOCz H5

60 .Oays

Days

Insecticide residues in citrus fruits 29

Fig. 18. Degradation and persistence curves for malathion on and in Valencia orange rind (see Table III); dosage: 0.8 lb. actual (25 percent wettable powder)/100 gallons, 2,500 gallons/acre [GuNTHER and CARMAN, Un­published (1958-1960), BLINN et al. 1959]

Fig. 19. Persistence curve of Morestan on and in Valencia orange rind (see Table III); dosage: one lb. actual (25 percent wettable powder) /100 gallons, 2,500 gallons/acre (HEARTH et al. 1966, GASTON et al. 1968). The former reference also lists residue persistence data from a two-lb. dosage as established by both colorimetric and oscillopolarographic methods. See also Figure 33 and associated discussion

Fig. 20

Fig. 20.

30

c

~ o Z 5

Clf"\. \J'O ...

CIO°.-CHZ

.... ........ 1 .... .. .. Navel oranges ....

Days

Degradation and persistence curves for Neotran on and in Eureka lemon and Valencia orange rind (see Table III); dosage: 0.5 lb. actual (40 percent wettable powder) /100 gallons, 1,500 gallons/acre (no longer used in California-Arizona citriculture) (JEPPSON et al. 1958)

30

Fig. 21

Fig. 22

-E Ii Ii

.! 'f o

2

F.A.GUNTHElt

t. Valencia oranges A-.... .... .... .... ..... .... .... .. ........ 6 Coulometric sulfur

...... I .... .... .... .... t ........

...... ......

9H3 H H 9 H3 c-c-T\..o-c.c-- O-S-O-CH2 -C=CH

I u '='Hz~ ):Hz

5.0

.... 1. E Ii Ii ,. ~ 0.5 o

CH3 C-C Hz HZ

60 Days

Whole-fruit basis

Days

1-......

Insecticide residues in citrus fruits 31

Fig. 21. Degradation and persistence curves for Omite on and in Valencia orange rind (see Table III); dosage: 0.5 lb. actual (57 percent emulsive con­centrate )/100 gallons, 1,500 gallons/acre [WESTLAKE et ai., Unpublished (1967) ]

Fig. 22. Degradation and persistence curves for ovex on and in Eureka lemons, whole-fruit basis; dosage: 0.5 lb. actual (50 percent wettable powder) / 100 gallons, 1,000 gallons/acre (GUNTHER and JEPPSON 1954). The orig­inal publication also includes residue persistence data for navel oranges (same dosage) and formulation and for lemons at 0.38 lb. actual (50 percent wettable powder)/loo gallons. See also Figure 28

Fig. 23

100

E Ii Ii ..

." c ::0

50

8. 10 E o u

0-I

3 5 o

CH3 ~ H3 C - CO(O- CHz - CH - 1.0 - S- 0 - CHz - CHz CI

I - I CH3 CH3

Days

Fig. 23. Degradation and persistence curves for OW-9 compounds (n = 2 and 3) on and in Valencia orange rind [see Table III and Section XI e)]; dosage: 10 oz. actual (85 percent emulsive concentrate)/100 gallons, 1,500 gal­lons/acre (experimental acaricide, never commercialized) [GUNTHER and JEPPSON, Unpublished (1962)]

32 F. A. GUNTHER

Fig. 24

2.0

E ci ci

c 0.5 0

...I:. -0 ... 0

0.

-__ Valencia oranges ----------------------- . . . ---------

Eureka lemons

0.1 0 20 40 60

Days

Fig. 25

4.0

3.0

CI-Q H H ,I 1 C-'C -CI

CI-Q/ CI

1.0 ~

E Q. Q. Valencia oranges

~ 0.5 I-

Whole-fruit basis

0.1L....._-L._---I __ ..L..._--L __ .L....._-L._---I o 20 40 60

Days

Insecticide residues in citrus fruits 33

Fig. 24. Degradation and persistence curves for parathion on and in Eureka lemons and Valencia oranges, whole-fruit basis; dosage: one lb. actual (25 percent wettable powder)!1 00 gallons, 1,500 gallons/ acre (current practices utilize not more than 0.6 lb. actual/lOO gallons) [GUNTHER and CARMAN, Unpublished (1949)]; see also ATKINS et al. (1961) for per­sisting residues on and in Valencia oranges at one, two, and four lb. of actual compound/ acre

Fig. 25. Degradation and persistence curves for TDE on and in Valencia oranges, whole-fruit basis; dosage: one lb. actual (50 percent wettable powder) / 100 gallons, 250 gallons/acre (ATKINS et al. 1961). The original publica­tion also includes residue persistence data from both half and double the above dosage

Fig. 26

-e ci ci

c 0 ~ -0

e Gi I-

7

6

5

4

3

2

CI~ CI-Q-S-OCf

Cf ~

Eureka lemons

Colorimetric

10~--~~--~--~60~~~--10~O---L--~140

Days

Fig. 26. Degradation and persistence curves for tetradifon on and in Eureka lemon rind (see Table III); dosage: four oz. actual (25 percent wettable powder)/lOO gallons, 1,500 gallons/acre [GUNTHER et al., Unpublished ( 1958)]; the original data included several dosages of both 25 and 50 percent wettable powders

34 F.A.GUNTHEB

appearance of the parent chemical still partly on the surface by de­posit-sloughing processes, weathering, and metabolic attack, whereas curve C represents persisting but still slowly degrading parent com­pound that has penetrated into and below the outer cuticular layers and is largely unavailable to other than metabolic attack by agents within the rind tissues.

The life histories of any metabolites that may be produced are best plotted arithmetically, especially if there is a general progressive succession of metabolites as with Di-Syston (at least four metabolites) (METCALF et al. 1967) and malathion (at least seven metabolites) (MENzm 1966). Systemic insecticides generally exhibit this different type of residue persistence, with a family of arithmetic curves repre­senting the disappearance of the parent compound, the appearance of a major metabolite and its conversion to second and perhaps third metabolites, etc., with consequent interdependent and usually con­stantly changing slopes.

b) Established persistenee curves

Those persistence curves which have been established for insecti­cides and acaricides on and in unwashed California citrus fruits are reproduced in Figures 3 through 26 in alphabetical order by current common or trade names. Some of these materials are no longer recom­mended or used in California citriculture, and for others the dosages recommended at the time have been decreased from those used for the preparation of these curves and in the initial petitions for tolerance assignments [see Section XI a) and especially Table XXVII]. These curves and their legends are largely self-explanatory; most of the pOints on each curve represent triplicated field samples, with the length of each vertical bar representing the maximum and minimum residue values for a particular sample. Frequent reference to particular curves to explain or illustrate points will be made throughout the re­mainder of the text.

c) Residue half-life concept

As was pointed out earlier, the slopes of persistence curves - and thus the "half-lives" 13 of the residues - are independent of the initial

13 The time required for half of the residue to lose its analytical identity whether through dissipation, attenuation, decomposition, metabolic alteration, or other factors. Alternate terminology that has been proposed by others is "residue­life 50 percent," or RL50• This concept and its reasonable applicability to residues persisting on and in plant parts have been discussed by GUNTHER and BLINN

(1955), HOSKINS (1961), GUNTHER (1962), FREAR (1963), and COOK (1965). Knowing the effective deposit and the half-life, a persistence curve of conservative utility can be constructed on semilog paper. Such a curve permits practicable extrapolations to a recognizedly approximate residue at any date after application of the pesticide. Similarly, a reliable persisting residue and its date plus the half­life permit loose extrapolation to probable earlier residues and their dates.

Tab

le I

V.

Per

sist

ence

hal

f-li

fe v

alue

s fo

r te

trad

ifon

res

idue

s o

n a

nd i

n th

e ri

nd a

t fie

ld-t

reat

ed l

emon

s an

d or

ange

s [G

UN

TIIE

R a

nd

c0

-

wor

kers

, U

npub

lish

ed (

19

58

)]

Dos

age

a

lIb

. 25%

W.P

./lO

O g

al.

2 lb

. 25%

W.P

./1

00

gal

.

Ana

lyti

cal

Yea

r m

etho

d H

alf-

life

H

alf-

life

E

ffec

tive

( d

ays)

E

ffec

tive

( d

ays)

de

posi

t /)

depo

sit

/) (p

.p.m

.)

Lem

ons

Ora

nges

(p

.p.m

.)

Lem

ons

Ora

nges

Infr

ared

19

56

4.7-

5.3

80

13

3 6.

5-8.

7 95

10

5 19

57

4.3-

4.9

82

-

5.0-

6.8

82

-

Col

orim

etri

c 19

56

4.0-

4.5

84

148

6.9-

7.5

80

10

6 19

57

3.4-

4.3

80

-

6.2-

7.9

78

-T

otal

chl

orid

e C

19

56

5.1

80

10

5 7.

2-7.

9 71

10

5 19

57

4.7-

5.6

81

-6.

9-8.

7 8

6

-8

1±

1

12

9±

16

8

2±

6

10

5±

1

a W

.P. =

wet

tabl

e po

wde

r.

/) B

ased

on

wei

ght

of u

nwas

hed

rind

onl

y. R

ange

rec

orde

d re

pres

ents

low

an

d h

igh

valu

es f

ound

. o

Tot

al o

rgan

ical

ly b

ound

chl

orin

e.

~ lb

. 50%

W.P

./lO

O g

al.

Hal

f-li

fe

Eff

ecti

ve

( day

s)

depo

sit

/) (p

.p.m

.)

Lem

ons

Ora

nges

4.0-

4.2

80

11

6 3.

0-3.

7 70

-

4.1-

4.6

78

12

5 4.

4-3.

6 7

4

-3.

9-4.

9 5

8

123

6.0-

7.6

72

-7

2±

5

12

1±

4

[ g ::t. ~ Ii f 8' t .... S. fir ~

36 F.A.Gt1NTHER

(effective) deposit, and thus also of dosage. These points are illus­trated in Table IV with data for the acaricide tetradifon (Tedion) [GUNTHER and co-workers, Unpublished (1958)] by three analytical methods applied to two field experiments in two successive years.

For a given compound on a given crop, the persistence half-life represents a characteristic, surprisingly constant value useful in broad comparisons of the persistences (longevities) of various pesticides on a single crop such as citrus fruits. Half-lives based upon persistence curves (C of Fig. 2) are acceptably constant, whereas those based upon degradation curves (B of Fig. 2) are markedly affected by the multitude of weathering processes in the field; thus, a rain within the degradation period will displace both Band C curves downward and may change the slope of B (but not of C).

If persistence curves are presented for more than one dosage, in addition to possibilities for extrapolation of residues to both earlier and later dates, there is also the possibility of interpolating for residues between dosages and of extrapolating with reservations to other dos­ages. Thus, as may be deduced from the discussions of EBELING (1963), deposit-vs.-dosage curves are not necessarily linear for most formula­tions. This fact is probably a consequence of the mechanics of deposit "build-up" on most plant sudaces, and is illustrated in Table V. With only two dosages, only occasionally are the initial deposits in the same arithmetic relationship as the dosages. From this table there are as many conformities as there are exceptions, but it seems clear that the higher the dosage the less reliable the initial deposit as a function of dosage. Because initial deposits are "built-up" of successive layers (EBELING 1963), they are unstable and tend to disintegrate and non­uniformly slough off as they dry. During the first two or three days after application, therefore, it is extremely difficult 14 to obtain reliable, uniform samples for initial deposit determinations (see Figs. 14 and 18, for example); it is probably much more realistic to extrapolate a suf-

14 No matter how carefully performed, even the mechanics of picking the sample will almost certainly dislodge variable amounts of initial deposits. Attempts to minimize this error have included snipping the 32-fruit samples directly into glass jars held in tum under each fruit, with subsequent careful rinsing of the jar with stripping solvent which is then pooled with the rind extractives. Also, the handling of fruits with fresh deposits on them, during weighing and peeling oper­ations, again increases the probabilities of erratic analytical results. This particular difficulty can be minimized with all samples by peeling them with rubber gloves over a small dishpan, then rinsing gloves, peeling tools, and pan with stripping solvent for subsequent pooling with the rind extractives [see section X d)2J. The value of any initial deposit determination remains obscure except in very general terms, even in comparing the depositing properties of different formulations unless credibility of a backwards extrapolation of a degradation curve (as in Table VI) is achieved through adequate sampling, replicates, and reproducibility.

Insecticide residues in citrus fruits 37

Table V. Illustrative general noncorrelation of initial deposits with dosages applied in the field

Average a initial deposit b

Dosage (p.p.m. on and in rind) Insecticide (lb. actual/ Reference

100 gal.) Lemons Oranges

Azinphos methyl 1 1.7 0.9 GUNTIlER et al. (1963) 3 3.5 2.0 4 4.4 3.5

Bidrin 0.5 - 2.1 MURPHY et al. 1.0 - 4.2 ( 1965 a and b) 1.5 - 6.1

Carbophenothion 0.25 4 4 GUNTHER et al. (1959 b) 0.75 18 12 1.5 21 21

DDT 2.5 a 6 2.0 GUNTHER et al., 5.0 0 6 4.0 Unpublished (1949),

10.0 c 16 4.0 CARMAN et al. (1950) Dioxathion 0.4 - 2.4 GUNTIlER et al. (1958 b)

0.8 8 4.8 1.6 13 8.3 3.2 21 -

OW-9 compounds 3 oz. - 14 GUNTIlER & JEPPSON, 5 oz. - 22 Unpublished ( 1962) 7 oz. - 28 9 oz. - 36

Parathion 0.25 - 1 ATKINsetaZ. (1961), 0.50 - 3 GUNTHER et al., 0.75 - 5 Unpublished (1950), 1.00 - 7 CARMAN et aZ., 1.25 - 10 Unpublished (1949) 1.50 - 12 14 0.8 0.5 2d 1.0 0.7 4 d 1.7 1.3

TDE 2.5 - 1.1 ATKINS et al. (1961) 5 - 2.4

10 - 3.0 Tetradifon 0.13 3.1 2.9 GUNTHER et al.,

0.25 4.3 3.6 Unpublished 0.50 4.4 6.8 ( 1958 and 1959)

a From three or more field-replicated samples. /) Sampled from within a few hours to three days after application. C Actual insecticide/acre. II Light coverage, skirt applications.

ficiently detailed degradation (not persistence) curve back to zero days, as in Figures 4 to 6, 10, 16, 20 to 23, and 25.

Also, on citrus fruits, emulsive formulations of a particular insecti-

38 F. A. GUNTHER

cide may deposit heavier than wettable powder formulations on lemons than on oranges, whereas with another insecticide the converse may be true; this point is illustrated by the data in Table VI (see also Fig.

Table VI. IUustrative noncorrelation of initial deposits with types of formulations

Average b initial deposit" Dosage Formu- (p.p.m. on and in rind)

Insecticide (lb. actual/ lation 11 100 gal.)

Lemons Oranges

Aramite 0.25 E.C. 4.5 -0.25 W.P. 3.4 -

Carbophen-othion 0.25 E.C. 6.1 10

0.25 W.P. 3.9 4.1 0.75 E.C. 21 19 0.75 W.P. 18 12 1.5 E.C. 38 40 1.5 W.P. 21 21

DDT 2 E.C. - 16 2 W.P. - 6

Diazinon 0.5 E.C. 9.2 4.0 0.5 W.P. 15 3.5

Dicofol 1.6 E.C. 14.5 7.4 1.6 W.P. 7.7 5.3

Dioxathion 0.4 E.C. 13 8.3 0.4 W.P. 9 3.6

Ethion 0.25 E.C. 4.4 4.7 0.25 W.P. 4.4 3.1

Heptachlor 0.5 E.C. 4.4 6.3 0.5 W.P. 3.8 9.0 2.0 E.C. 6.0 -2.0 W.P. 8.0 -

11 E.C. = emulsive concentrate, W.P. = wettable powder. b From three or more field-replicated samples.

Reference

GUNTHER et al. (1957 a)

GUNTHER et al. (1959 b)

CARMAN et al. (1950)

GUNTHER et al. (1958 a)

GUNTHER et aZ. (1957 b)

GUNTHER et aZ. (1958 b)

GUNTHER et aZ. (1962 b)

GUNTHER & CARMAN, Unpublished (1954)

C Sampled from within a few hours to three days after application. Valuei ob­tained by backwards extrapolations of the degradation curves.

17) obtained by the backwards extrapolations of the degradation curves.

That the slopes of persistence curves - and thus half-life values­are usually independent of formulation (e.g., wettable powders vs. emulsive concentrates) is illustrated in Figure 17 for the same dosage of wettable powder and emulsive concentrate formulations of hepta­chlor on and in the rind of Eureka lemons. Both curves have the same slope and therefore both formulations have the same half-life of about 23 days. GUNTHER and BLINN (1955) and EBELING (1963) discuss this observation in considerable detail.

Insecticide residues in citrus fruits 39

The U.S. Food and Drug Administration (see COOK 1965) has stated that persistence curves, when the points comfortably fit the line, confer a great deal of credibility to each experiment under the con­ditions that prevailed. The warning is expressed, however, that so many difficult-to-control important variables are involved in the deposition and residue persistence phenomena that it may be "hazardous to at­tempt to relate persistence curves to each other or to assure that one can make an individual analysis and place it on a persistence curve to determine quantitatively what happened before and to predict what will happen." Nevertheless, persistence curve comparisons for various insecticides on and in a single variety (e.g., Washington navel oranges, Valencia oranges, Eureka lemons) can be productive of much useful and credible information, especially when supported by the present abundant evidence for lemons and oranges as the substrate.

d) Uses of half-lives and persi3tence curves

The half-life values of 28 insecticides and five model polynuclear hydrocarbons 15 on lemons and oranges are collated in Table VII.

Some of the generalities about persistence half-lives are illustrated in the preceding figures. Figure 10 is the curve for DDT, as an illustra­tion of an organochlorine insecticide, on a whole Valencia orange basis; at the dosage used (10 lb. of 50 percent wettable powder/acre), the present tolerance of 1.0 p.p.m. is met at about the 30-day interval. Figure 5 represents an organophosphorus compound, Bidrin, on and in mature orange rind; as a somewhat less persistent insecticide, its toler­ance (temporary to June 1968) of 0.25 p.p.m. on a whole-fruit basis is met after about 22 days with the dosage shown. Figure 8 represents another type of organochlorine compound, chlordane, on and in mature lemon rind; at the dosage given, its tolerance of 0.3 p.p.m. on a whole­fruit basis is not met until about 70 days after application. Figure 22 represents an organohalogen sulfonate compound, ovex, also on and in mature lemon fruit; its tolerance of five p.p.m. is not exceeded by the dosage utilized. DDT, Bidrin, and chlordane generally have degrada­tion half-lives of less than 10 days, whereas that for ovex is from 10 to 20 days, possibly illustrating faster penetration into the rind with conse­quent "protection" of the ovex residue (cf. Table XVII and Fig. 28).

As was shown in Figure 25, the degradation-persistence curves for TDE on and in oranges are almost superimposable upon those for DDT (Fig. 10), as might be expected based upon near identity of the two

15 In reference to possible polynuclear hydrocarbon components of some spray oils.

40 F. A. GUNTHER

Table VII. Persistence half-life values of insecticides on and in citrus fruits

Half-life (days) Insecticide Reference

Lemons Oranges

Anthracene a -175 GUNTHER et al. (1967) Aramite - 13 > 30 GUNTHER & JEPPSON (1951) Azinphos methyl - 38 -355 GUNTHER et al. (1963) Benzopyrene II -175 GUNTHER et al. (1967) Bidrin - 15 MURPHY et al. (1965 a and b) Carbaryl - 28 - 42 GUNTHER et al. (1962 a) Carbophenothion - 22 - 42 GUNTHER et al. (1959 b) Chlordane 19 19 BLINN et al. (1959 a) Chlorobenzilate 66 - 66 BLINN et al. (1954),

GUNTHER et al. (1955) DDT 30 - 50 GUNTHER et al. (1946),

ATKINS et al. ( 1961) Demeton - 30 METCALF et al. (1954 band 1955) Diazinon - 13 - 17 GUNTHER et al. (1958 a) Dibenzanthracene II -120 GUNTHER et al. (1967) Dibenzopyrene II - 12 GUNTHER et al. (1967) Dicofol -125 -200 GUNTHER et al. (1957 b) Dieldrin - 60 -60 BLINN et al. (1959 a) Dimethoate - 19 GUNTHER et al. (1965) Dioxathion - 70 >100 GUNTHER et al. (1958 b) EPN - 80 - 50 GUNTHER & CARMAN,

Unpublished ( 1955); GUNTHER & JEPPSON, Unpublished (1960)

Ethion - 30 - 42 GUNTHER et al. (1962 b) Heptachlor - 23 - 23 BLINN et al. (1959 a) Malathion - 32 BLINN et al. (1959 a) Methylcholanthrene II -200 GUNTHER et al. (1967) Mevinphos - 2 ATKINS et al. (1961) Morestan - 37 - 36 GASTON et al. (1968) Neotran - 30 - 39 JEPPSON et al. (1958) Nicotine 5 GUNTHER et al.,

Unpublished ( 1942 and 1958) Omite 75 GUNTHER et al.,

Unpublished ( 1966) Ovex 10-30 10- 25 GUNTHER & JEPPSON (1954) OW-9 compounds c 85-130 GUNTHER & JEPPSON,

Unpublished ( 1963) Parathion - 60 >100 CARMAN et al. (1950),

EWART et al. (1951), ATKINS et al. (1961)

TDE > 42 ATKINS et al. (1961) Tetradifon 79 ± 6 -130 GUNTHER et al.,

Unpublished (1960)

a Indicator (reference) polynuclear hydrocarbon for footnote h. II As model polynuclear hydrocarbons to evaluate probable behaviors of those

polynuclears that are in some spray oils (GUNTHER and BUZZETTI 1965, GUNTHER etal.1967).

c See Table XXX.

Insecticide residues in citrus fruits 41

insecticides; the United States tolerance for TDE is currently 7.0 p.p.m. That it is not safe, however, to assume nearly identical degradation­persistence curves for nearly identically structured pesticide chemicals is clearly illustrated by the curves for Aramite (Fig. 3), the OW -9 com­pounds (Fig. 23), and Omite (Fig. 21); degradation half-lives on and in oranges are approximately five, 25, and 15 days, respectively, and persistence half-lives are approximately 30, 160, and 75 days, respec­tively, for these three acaricides (see Table VII).

e) Effects of variety on residues

The effect of citrus variety on slope of persistence curve and, there­fore, on half-life is not predictable, as illustrated in Tables V, VI, and VII and in earlier detail in Figure 6 with a carbamate (carbaryl), in Figure 24 with an organophosphorus compound (parathion), in Figure 20 with an organochlorine compound (N eotran), and in Figure 11 with a heterocycle-organophosphorus compound (diazinon) on both lemons and oranges. With the possible exception of Neotran, the two persist­ence curves for a given insecticide are parallel, but among these four compounds, the oranges twice accepted the greater deposit from the same formulations and the lemons twice; especially great differences between varieties are apparent with diazinon. The varietal influence on the persistence of insecticides is also illustrated in Table VIII show-

Table VIII. VarietaZ influence on magnitudes and persistences of residues of para­thion [CARMAN et aZ. 1950, GUNTHER et aZ., Unpublished (1950)]

Harvest residue b (p.p.m.)

Dosage a Oranges (oz.j100 gal.) Eureka

Navel I Valencia lemons

2 0.1 0.1 4 1.7 0.7 8 2.5 1.9 2.1

12 4.2 3.5 16 < 5.2 4.3 2.6 20 7.0 6.4 4.4 24 11.3 8.1

a Actual compound, from a 25 percent wettable powder. b From 30 to 40 days after treatment. C Cf. Table IX.

Marsh grapefruit

1.5

4.9. 6.9

ing the harvest residues of parathion in the rinds of four citrus varie-

42 F. A. GUNTHER

ties from diHerent dosages of the same formulation. Except for the residue from the 24-ounce dosage on navel oranges, both sets of orange data plot arithmetically as parallel straight lines, showing no differ­ences between orange varieties; the limited lemon and grapefruit data do not fit an arithmetic plot.

Citrus variety also influences eHective deposits and, therefore, har­vest residues, as illustrated in Table IX. EHective deposits are conveni­ently obtained by extrapolating persistence curves back to zero day after treatment.16

V. Insecticide residues in citrus products

Normally, those citrus fruits not destined for the fresh fruit market are converted into a variety of major products, including canned and frozen juices and juice concentrates, dried citrus pulp cattle feed, and citrus oils; lesser products are citrus marmalade, dried and candied rind for confectioner's uses, and others including some pharmaceutical products. Citrus molasses is not a product of the California industry. ANDERSON et aI. (1963) have reported in detail on residues of azinphos methyl on and in washed and unwashed pineapple oranges and the products juice, dried citrus pulp cattle feed, oil, and molasses; their data agree with those herein presented for this insecticide.

a) Citrus juices

As mentioned early in this manuscript, prior to the commercial utilization of the pest-control agent, its residues on and in citrus fruits are established separately in rind versus "pulp" 17 rather than in the ground whole fruit. It will be recalled that the tolerances for pesticides on and in citrus fruits are on the whole-fruit basis, and both surveil­lance and monitoring market-control residue analyses are accordingly usually made on the ground whole fruit. Because of our interest in evaluating rates and extents of insecticide penetration into citrus fruits on the tree, our laboratories have consistently separated the rind from the fruit and analyzed each separately. Insecticide found in the washed, albedo-free peeled fruit, therefore, may be considered to have pene­trated into the juice while the fruit was intact. Juices prepared by means of a mechanical squeezer (corrugated rolls, screw presses, etc.)

16 Similar extrapolation of degradation curves yields initial deposits; see foot­note 14.

17 The peeled fruit, freed from albedo and scrupulously cleansed before cylin­drical plugs of "pulp" are cut out for juice analyses [see section X d)].

Tab

le I

X.

Var

ieta

l in

flue

nces

on

eff

ecti

ve d

epos

its

of

vari

ous

inse

ctic

ides

Rin

d de

posi

t (p

.p.m

.)

Dos

age

a D

ays

(oz.

/10

0

to

Val

enci

a N

avel

E

urek

a In

sect

icid

e ga

l. )

sam

plin

g or

ange

s or

ange

s le

mon

s R

efer

ence

Ara

mit

e 3

W.P

. 1

-0.

9 0.

9 G

UN

THER

et a

Z. (

19

51

) A

zinp

hos

met

hyl

4W

.P.

1 0.

9 -

1.6

GU

NTH

ER e

t al.

(19

63

) 1

2W

.P.

1 2.

0 -

3.5

16

W.P

. 1

3.5

-4.

3 B

idri

n 4

W.P

. 5

3.3

-5.

0 G

UN

THER

et a

Z. (

19

63

) 1

2W

.P.

5 6.

8 -

10

16

W.P

. 5

15

-13

C

arba

ryl

8W

.P.

2 9.

1 -

9.5

GU

NTH

ER e

t aZ.

(1

96

2 a

) 1

6W

.P.

2 17

-

17

DD

T

32

W.P

. 2

5.8

5.6

5.6

CA

RM

AN

et a

l. ( 1

950)

3

2E

.C.

2 16

14

12

1

6E

.C.

1 11

3.

9 7.

5 D

iazi

non

4W

.P.

1 0.

6 -

6.0

GU

NTH

ER e

t aZ.

(1

95

8 a

) 4

E.C

. 1

1.0

-4.

0 D

icof

ol

4W

.P.

1 6.

0 -

7.5

GU

NTH

ER e

t aZ.

(1

95

7 b

) 4

E.C

. 1

7.6

-12

D

ioxa

thio

n 6

W.P

. 1

-1.

1 4.

8 G

UN

THER

et a

Z. (

19

58

b)

3 E

.C.

1 -

7.2

2.7

6E

.C.

1 -

12

7 12

E.C

. 1

-20

9

Eth

ion

4W

.P.

5 4.

2 -

4.5

GU

NTH

ER e

t aZ.

(1

96

2 b

) 1

6W

.P.

5 23

-

10

3 E

.C.

5 6.

4 -

4.4

Neo

tran

8

W.P

. 2

-12

15

JE

PPSO

N e

t al.

( 19

58

) O

vex

4W

.P.

1 6.

0 -

6.1

GU

NTH

ER &

JEP

PSO

N (

19

54

) P

arat

hion

1

6W

.P.

2 9.

8 11

.8

6.8

CA

RM

AN

et a

l. (1

95

0)

Sch

rada

n _

b

1 0.

9 -

0.7

MET

CA

LF e

t al.

(19

52

) ------

a W

.P. =

wet

tabl

e po

wde

r, E

.C. =

em

ulsi

ve c

once

ntra

te.

Oun

ce v

alue

s re

pres

ent

wei

ghts

of

actu

al c

ompo

und

used

. b

0.1.

per

cen

t aq

ueou

s so

luti

on c

onta

inin

g a

surf

acta

nt.

I-<

&l ~ o· g: ~ g: ~ s· (

) ~ [ 1t "'" CN

44 F. A. GUNTHER

or reamer will contain some citrus oils 18 and some albedo and rag,19 and some commercially prepared juices may even contain "rinsings" from the washed rind as the expressed juice flows over crushed pieces of it. Since most insecticides are readily soluble in citrus oils (see also footnote 23) and since penetrated residues of these chemicals are be­lieved to be largely in the oil sacs in the rind, it is clear that juices prepared in the laboratory in the manner described should be freer of insecticide residues than commercially prepared juices. The data in

Table X. Some insecticide residues in citrus iuices (sources are those listed for the corresponding compounds in Tables V through IX)

Maximum residue

Insecticide Fruit No. How (p.p.m.)

samples prepared a

Rind b I Juice b

Aldrin Oranges 2 Com. - <0.1 Aramite Oranges 4 Com. - <0.1 Azinphos methyl Lemons 15 Lab. 14 <0.1

Oranges 30 Lab. 19 <0.1 Bidrin Oranges 63 Lab. 7.2 0.1 Carbaryl Lemons 7 Lab. 21 <0.2 0

Oranges 7 Lab. 19 <0.2 0

Carbophenothion Lemons 36 Lab. 23 0.02 Oranges 36 Lab. 21 0.02

Chlordane Lemons 21 Lab. 9.0 <0.1 Chlorobenzilate Lemons 36 Lab. 20 <0.2 DDT Oranges 26 Lab. 10 <0.1

Oranges 26 Com. - -5 Diazinon Lemons 11 Lab. 12 <0.1

Oranges 14 Lab. 4.4 <0.1 Dicofol Lemons 19 Lab. 16 0.05

Oranges 56 Lab. 11 0.15 Dieldrin Lemons 5 Lab. 6.8 <0.1

Oranges 33 Lab. 0.8 <0.1 Oranges 6 Com. - 0.1

Dimethoate Oranges 60 Lab. 16 <0.1

18 Desirable from a consumer-acceptance standpoint. According to SWISHER

( 1968) modem juice extractors incorporate very little oil from the rind. Addition­ally, current juice processing methods can involve (if required) removal of much entrained oil by high-speed centrifugation. Commercial juice with high rind oil content has sometimes been put through a flash evaporator (deoiler) to reduce oil content. One widely used modern extractor simulates hand burring by means of a rotating reamer and thus offers little opportunity for the juice to lave crushed oil­containing rind tissues. The amount of citrus rind oil in juice products as consumed is obviously self-limiting, however, with an upper limit of about 0.02 percent; in baby foods the rind oil is usually less than 0.003 percent (SWISHER 1968).

19 Internal connective tissues and membranes.

Insecticide residues in citrus fruits 45

Table X. (Continued)

Dioxathion Lemons 40 Lab. 25 0.03 Oranges 40 Lab. 9.7 0.03

EPN Oranges 2 Lab. 3.1 <0.1 Oranges 9 Com. <0.1

Ethion Lemons 15 Lab. 10 <0.2 Oranges 16 Lab. 32 <0.2

Heptachlor Lemons 12 Lab. 10 <0.2 Malathion Lemons 6 Lab. 4.8 0.03

Oranges 77 Lab. 4.1 0.1 Neotran Lemons 6 Lab. 16 0.0

Oranges 6 Lab. 15 0.2 Omite Oranges 10 Lab. 9.0 <0.2 Ovex Lemons 11 Lab. 6.4 0.4

Oranges 12 Lab. 2.3 <0.1 Oranges 3 Com. 0.4

Parathion Grapefruit 31 Lab. 0.6 <0.05 Lemons 8 Lab. 3.8 <0.05 Oranges 54 Lab. 6.0 <0.05 Oranges 116 Com. 0.4 a Oranges 16 Com.e 2.0t

Tetradifon Lemons 27 Lab. 11 <0.03 Oranges 21 Lab. 11 <0.03

a Lab. = laboratory, Com. = commercial. b If laboratory, rind and juice values are from the same fruits, about 30 days

after treatment. c <0.1 p.p.m. of a-naphthol, also. a Average 0.1 p.p.m. e Commercial frozen concentrate. f A single sample read 22 p.p.m.

Table X demonstrate this differential in "contamination." Most of the values reported are well above the minimum detectabilities of the ana­lytical methods used. The DDT and parathion in the commercially prepared juices undoubtedly originated from the oil (cf. Table XVII), whereas the ovex may have actually penetrated into the pulp of the treated fruits (cf. Tables X and XVII and Fig. 28).

It is surprising that carbaryl, with a water solubility of about 40 p.p.m. (GuNTHER et al. 1968) at 25° G, does not appear in juice in greater amounts; in the laboratory-prepared juice the free a-naphthol from possibly in situ hydrolyzed carbaryl was less than 0.1 p.p.m. That there is no general correlation between amounts of residues present in laboratory-prepared juice and the numerical reported solubilities in water at about 25° C. is demonstrated by the data in Table XI.

Practically nothing is known about the occurrence of metabolic or other alteration products [see section XI c)] of these generally non­systemic insecticides in either laboratory-prepared or commercial juices. The one notable exception is the carbamate insecticide carbaryl, where

46 F.A.GUNTHER

Table XI. Reported water solubilities of some insecticides and amounts found in citrus iuices (from Table X)

Solubility in

Insecticide water a (p.p.m.)

Aldrin 0.2 Aramite "Insoluble" Azinphos methyl ,...,33 Bidrin Miscible Carbaryl 40 Carbophenothion 0.34 Chlordane "Insoluble" Chlorobenzilate "Insoluble" DDT ,...,0.003 Diazinon ,...,40 Dicofol "Insoluble" Dieldrin 0.25 Dimethoate ,...,20,000 Dioxathion "Insoluble" EPN "Insoluble" Ethion 2 Heptachlor "Insoluble" Malathion 145 Neotran "Insoluble" Omite Ovex "Insoluble" Parathion ,...,25 Tetradifon <200

a At 25° C. From GUNTHER et al. (1968). b Lemon or orange; maximum level found (from Table X). o Commercially prepared juice. d ANDERSON et al. found traces in Florida oranges.

Amount found in

juice b

(p.p.m.)

<0.1 0 <0.1 0

<0.1 d

0.1 <0.2

0.02 <0.1 <0.2 ,...,5 0

<0.1 0.15 0.10

<0.1 0.03

<0.1 0 <0.2 <0.2

0.1 0.2

<0.2 0.4 0 2.0 0

<0.03

< 0.2 p.p.m. of the unchanged compound was accompanied in the laboratory-prepared juice by < 0.1 p.p.m. of its expected major hydroly­sis product, a-naphthol. Parathion is only a weak anticholinesterase agent, whereas its in situ 20 metabolite paraoxon is nearly 1,000 times more active. The solubility of the former in water is about 25 p.p.m. and of the latter about 2,400 p.p.m. (GUNTHER et al. 1968), yet nothing has been published about possible paraoxon residues in citrus juices; paraoxon is generally short-lived in living tissues, but it might be much more persistent in acidic citrus juices and especially in the presence of the "protective" traces of citrus oils in commercial juices [see section XIc)].

20 In both plant and animal tissues,

Insecticide residues in citrus fruits 47

As can also be discerned from the data in Table X, there is no ap­parent correlation between the maximum residues found in the labora­tory-prepared juices and the residue loads in the rinds of the juiced fruits. As pointed out earlier, with enough commercially prepared samples, these two types of data almost certainly should correlate be­cause of the opportunities for contamination of some commercial juices by rind components, especially the rind oil which seems to be the highly stable reservoir for these penetrated nonsystemic insecticides.

The effects of vacuum concentration [up to 72° Brix (SWISHER 1968 )] upon any pesticide residues that might be present in commer­cial citrus juices are not known (except for parathion; see Table X and footnote e). It may be conjectured, however, that this essentially steam-distillation process could remove some of any pesticide residues present.

b) Laboratory-prepared citrus pulp cattle feed

1. Preparation 21, - From two to four field boxes (from about 75 to 150 pounds) of representative tree-ripe fruits 22 are weighed and sub­merged two to three minutes in a 0.5 percent special packing-house soap (50 percent soap and 50 percent sodium carbonate) solution at 110° to 112° F.; each fruit is then brushed lightly but completely, rinsed thoroughly with clear tap water followed by distilled water, and allowed to dry at room temperature. Each fruit is halved and juiced on a power juicer. The remaining hemispheres of rind are weighed and finely ground (~- to *-inch mesh) in a power grinder (not chopper) so as to crush most of the cells for satisfactory enzyme action in the next operation.

Dry hydrated lime at the rate of six g.jkg. of lemon rind or eight g.jkg. of orange rind is then sifted over a seven-kg. aliquot of the ground rind puree with prompt and thorough mixing. The limed rind mixture is allowed to stand until it has hardened with a glazed, crisp appearance and a clear serum can be readily squeezed out: normally,

21 As approved by Sunkist Growers, Inc., and accepted by the U.S. Food and Drug Administration for the laboratory-scale preparation of a product that ac­ceptably simulates the California commercial product with reference to intended pesticide residue evaluations. This procedure was designed with the cooperation of the Research Department of Sunkist Growers, Inc., Ontario, California. In the commercial process, liming of the rind may be slightly higher if products such as the Havonoids are to be recovered before the product goes to the direct gas-fired rotary kiln dryer. Temperatures of the rind as it travels through a dryer are not known, but the product does not char or caramelize appreciably; a forced-ventila­tion oven probably rather closely approximates opportunities for volatilization and steam distillation of susceptible chemicals present in the ground and limed rind.

22 Oranges may be processed at once. Lemons should be allowed to stand at room temperature for a few days. Only tree-ripe fruits should be used.

48 F. A. GUNTHER

about 30 minutes are required. At this stage the limed rind mixture should no longer be alkaline (from an original pH of about 12 to a final pH of 5.0 to 6.5); if the pH is too low, more lime is added with stand­ing for another 30 minutes.

Using a tapered-screw press (Hobart type D), the limed rind mix­ture is pressed, with the press well loaded at all times to obtain a mod­erately dry pulp. The products of this operation are a dilute emulsion of rind oil in the rind serum, which is discarded, and the wet pulp of about 40 percent moisture content. The pulp is dried at least overnight in a moderately vented oven at 60° to 65° c., or preferably in a low­draft, forced-ventilation oven at 60° to 65° C. to a moisture content (Dean-Stark method) of from eight to ten percent. The samples of pulp are best dried in cheese-cloth-lined baskets with a pulp depth of not more than one inch. Samples containing more than about ten percent moisture do not store well (see footnote 37 for analytical proc­essing of this product).

Washed fruit (100%)

I ~""----II Juicing machine It----'l

Unfiltered juice Rind (63.2°.4) (36.8%)

~ ~ Juice ·Pulp" Pressed rind Raw ail (50%) (6%) (34%) (5%)

Oil "pUlp" Oil

Pressed rind (40%)

Dried pulp (7%)

(0.1-0.5%)

Press liquor (6%)

Fig. 27. Flow diagram and approximate yields of products from the commercial processing of oranges into juice, oil, and dried orange pulp cattle feed [Sunkist Growers, Inc., Personal communication (1958) 1

Insecticide residues in citrus fruits 49

The commercial process for making dried citrus pulp cattle feed is diagrammed in Figure 27. Indicated yields are approximate. The above laboratory procedure for preparing this product simulates this com­mercial process as closely as possible except for returning some juice solids and the "pulp" recovered from the crude oil to the pressed rind before the liming operation.

2. Residues. - Those insecticide residues found in this type of laboratory-prepared citrus pulp cattle feed from California field resi­due programs to date are collated in Table XII. Unfortunately, many of the insecticides that have been used commercially in citriculture have not been investigated as possible components of citrus pulp cattle feed, or the residue data that may have been developed by the agricul­tural chemicals industry have not been published.

The whole rind, as peeled from the fruits, normally has a moisture content of 70 to 85 percent, the limed-and-pressed rind ("wet pulp") contains about 40 percent moisture, and the final product ("dried pulp") averages about nine percent moisture. There is thus a potential residue-concentration factor of two in going from rind to limed-and­pressed rind, and an additional four-fold concentration in going from this stage to the final product; the overall potential residue-concentra­tion factor from fresh rind to citrus pulp cattle feed is therefore about eight. Thus, rind residues multiplied by eight would approximate the maximum residue that could occur in the final dried product. Since the rind represents from ~~ to )& (see Table III) the weight of the whole fresh fruit (moisture contents: lemons,..... 83 percent, oranges ,..... 80 per­cent), multiplying the residue on a whole-fruit basis by about 32 simi­larly would provide an estimate of the maximum residue that could occur in dried citrus pulp cattle feed made from those fruits.

However, as can be seen from Table XII, this "carry-over" of total residue load to final dried product has never occurred with the insecti­cides evaluated. On the contrary, there are usually great losses, during the preparation of this product, by way of the discarded press liquors 23

from the liming operation and during the drying process. An extreme example from this table is malathion, which is practi­

cally quantitatively lost during the liming operation. From the avail­able data, other examples of insecticides that do not tolerate the liming operation are azinphos methyl, carbaryl, dicofol, and Morestan. The overall procedure destroys most of the DDT, DN-lll, ethion, Omite, parathion, and tetradifon residues, as well. In this list, dioxathion is the only insecticide that survives the total procedure without major losses.

23 The press liquors are essentially dilute emulsions of the citrus oils in water and, in general, citrus oils (about 85 percent limonene) are excellent solvents for most organic insecticides.

Tab

le X

II.

Inse

ctic

ide

resi

dues

in

labo

rato

ry-p

repa

red

citr

us p

ulp

catt

le f

eed

from

com

mer

cial

-typ

e tr

eatm

ents

Res

idue

(p.

p.m

.) i

n

Inse

ctic

ide

Fru

it

Ref

eren

ce

Who

le r

ind

Wet

pu

lp

Dri

ed p

ulp

(n

o. o

f sam

ples

) (n

o. o

f sa

mpl

es)

(no.

of

sam

ples

)

Azi

npho

s m

ethy

l L

emon

s 9.

4 ±

0.4

(6)

a 3.

5 ±

0

.3(6

) 5.

6 ±

0.7

(4)

GU

NTH

ER e

t al.

(19

63

) O

rang

es

4.3

± 0

.1(3

) a

0.7

± 0

.1(3

) 1.

4 ±

0.0

(3)

GU

NTH

ER e

t al.

(19

63

) O

rang

es

1.7

b -

1.5

AN

DER

SON

et

al.

(19

63

) B

idri

n O

rang

es

8.6

± 0

.6( 6

) b

7.3

±

0.1

(6)

2.4

± 0

.2(6

) M

UR

PHY

et a

l. (1

965

b)

Ora

nges

3.

9 ±

0.7

(3)

a -

4.2

± 0

.3(3

) M

UR

PHY

et a

l. (1

965

a)

Car

bary

l O

rang

es

15.9

± 2

.2(6

) a

1.6

±

0.2

(6)

2.0

± 0

.7(5

) 8

GU

NTH

ER e

t al.,

U

npub

lish

ed (

196

1)

DD

T

Ora

nges

3

-13

(6)

c,a

-1

-10

(6)1

G

UN

THER

et a

l.,

Unp

ubli

shed

(1

95

1)

Dic

ofol

L

emon

s 4

-12

( 4

) c

-7

-14

(8)

GU

NTH

ER e

t al.

(19

57

) O

rang

es

5-9

(11

) c

-8

-17

(11

) G

UN

THER

et a

l. (1

957

b)

Ora

nges

1.

3 ±

0.1

(6)

a 0.

5 ±

0

.0(6

) 1.

3 ±

0.1

(6)

GU

NTH

ER &

JEP

PSO

N,

Unp

ubli

shed

( 1

956)

D

imet

hoat

e O

rang

es

4.7

± 0

.5(4

) a

2.6

±

0.4

(4)

2.9

± 0

.6(6

) G

UN

THER

et a

l. (1

96

5)

Dio

xath

ion

Lem

ons

7.6

± 0

.4(6

) a

-41

.6 ±

2.

6( 4

) G

UN

THER

et a

l. (1

958

b)

Ora

nges

2.

6 ±

0.3

(6)

b -

2.1

± 0

.2(6

) G

UN

THER

et a

Z.,

Unp

ubli

shed

( 1

958)

D

N-l

l1

Ora

nges

1.

6 ±

0.3

(10

) a

1.l

±0

.2(6

) 0.

9 ±

0.1

(6)

GU

NTH

ER &

CA

RM

AN

, U

npub

lish

ed (

19

66

) E

thio

n O

rang

es

4.8

± 0

.4(3

) a

-1

.l±

0.2

(3)

GU

NTH

ER e

t aZ.

, U

npub

lish

ed (

19

61

) M

alat

hion

O

rang

es

7.0

±

0.2

(5)

a <

0.2

(5)

<0

.2(5

) G

UN

THER

& C

AR

MA

N,

Unp

ubli

shed

(1

96

1)

Mor

esta

n O

rang

es

3.8

± 0

.2(4

) a

1.0

±

0.3

(6)

1.0

± 0

.2(6

) G

AST

ON

et a

Z. (

196

8)

C1l.

o ~

~ f

Tab

le X

II.

(Co

nti

nu

ed)

Res

idue

(p

.p.m

.) i

n

Inse

ctic

ide

Fru

it

Wh

ole

rin

d ( n

o. o

f sa

mpl

es )

Om

ite

Ora

nges

4.

5 ±

0.3

(6)

a

Par

athi

on

Lem

ons

1-5

(6)c

,a

Ora

nges

1

-6(1

8)

c,a

Tet

radi

fon

Lem

ons

16.6

± 0

.4(2

) a

Ora

nges

10

.7 ±

0.2

(13

) a

a A

ppro

xim

atel

y 30

day

s af

ter

trea

tmen

t.

b A

ppro

xim

atel

y 15

day

s af

ter

trea

tmen

t.

c O

ver

seve

ral y

ears

, var

ious

har

vest

dat

es a

fter

app

lica

tion

. a

Var

ious

har

vest

dat

es a

fter

app

lica

tion

. e

Als

o co

ntai

ned

0.9

± 0

.2( 6

) p.

p.m

. of

fre

e a-

naph

thol

.

Wet

pu

lp

(no.

of

sam

ples

)

2.5

± 0

.2(6

)

- - -

0.8

± 0

.2(

10

)

Ref

eren

ce

Dri

ed p

ulp

(n

o.

of s

ampl

es)

3.4

± 0

.1(6

) JE

PP

SO

N e

t al.,

U

npub

lish

ed (

196

7)

1-6

(6

)

GU

NT

HE

R e

t al.,

U

npub

lish

ed (

195

0)

1-1

0(3

0)

GU

NT

HE

R e

t al.,

U

npub

lish

ed (

19

50

) 0.

5 ±

0.0

(3)

GU

NT

HE

R e

t al.,

U

npub

lish

ed (

19

58

) 0.

8 ±

0.3

( 1

0)

GU

NT

HE

R e

t al.,

U

npub

lish

ed (

19

58

)

f R

esid

ues

in f

eed

from

th

e cu

rren

t co

mm

erci

al p

rodu

ctio

n ra

nge

from

non

e de

tect

able

to

abo

ut

0.3

p.p.

m.

(SW

ISH

ER

19

68

).

r n go g: ~ t s· n [ 2' ~ t1l

......

52 F. A. GUNTHER

Carbaryl was partially hydrolyzed to a-naphthol during the liming and drying operations (see footnote e, Table XII).

c) Citrus oils

1. Preparation. - Commercially produced citrus oils from washed fruits are obtained from the rind with various types of roller, screw, or other presses. Initially, these presses yield a dilute "milk," or oil-in­water emulsion, which is filtered and centrifuged to a thick "cream," then to clarity and homogeneity in a high-speed centrifuge. The result­ing clear oils are cured or "fined" by storage at 60° to 70° F. for some weeks to allow semidissolved proteins, waxes, and other colloidally­dispersed material 24 to coagulate and precipitate, then are recentri­fuged. These so-called "cold pressed" oils, or U.S. Pharmacopoeia (U.S.P.) grade oils, are excellent solvents for many pesticides,23 and this manufacturing process would not be expected to decompose or otherwise alter any contained pesticides except for possible losses by coprecipitation during the curing operation. In the laboratory, these oils may be duplicated in low but analytically adequate yields by plac­ing one or two kg. of ground rind from mature fruits in a thick, closely woven borosilicate-glass-cloth bag, pressing it at 15,000 to 20,000 lb./sq. inch, and filtering and centrifuging the resulting press liquid to clarity and homogeneity. Alternatively and with higher yields, wire brush scrapings of the flavedo layer can be pressed.25

2. A, B, C, residues. - As was stated earlier,23 most of the non­systemic insecticides are readily soluble in these oils. In aged residues they presumably, and for the larger part, are dissolved in these oils in the oil sacs of the rind, as reasonably indicated by residue persistence curves such as those shown earlier in Figures 3 through 26, based upon ground rind extracted with an organic solvent. Further credence is given this probability that most nonsystemic insecticides in aged resi­dues have migrated into the oil sacs by the "A, B, C techniques" of GUNTHER and BLINN (1955). This terminology results from the arbi­trary segregation of aged (penetrated) residues in citrus rind into three types:

Type A = extracuticular residue, or residue adhering to the wax layer. This

24 Stearoptenes, or all foreign material not completely oil-soluble. 25 A small, motor-driven wire brush is mounted almost Hush with a small,

wooden or plastic platform containing an opening that just clears the brush. Fruits are pushed across the brush, rotated slightly to expose a fresh area, brushed again, etc. These brushings yield more oil than ground rind because of the absence of the very porous albedo. This technique was designed by C. W. WILSON, Sunkist Growers, Inc., Ontario California.

Insecticide residues in citrus fruits 53

residue represents the true initial deposit, effective deposit or residue, or surface residue as discussed earlier. It is approximated by thor­oughly washing the whole fruit, with gentle brushing with a soft brush, with 0.2 percent detergent solution followed by extraction of the washings with a suitable organic solvent.

Type B = cuticular residue, or residue embedded within or dissolved in the rind surface waxes. In some instances, this residue may also be part of the effective residue, i.e., it may still be biologically effective against some insect and mite species. It is approximated by quick laving of the air-dried fruit from A with a suitable organic solvent.

Type C = subcuticular residue, or residue penetrated below the wax "layer" of citrus fruits. This category may be further subdivided, if desired, into flavedo ( pericarpal) residue versus albedo residue. It is ap­proximated by thorough solvent equilibration of the ground rind or, separately, the ground flavedo and the ground albedo.

Three examples of the "A, B, C persistence" curves obtained by this technique are reproduced in Figures 28, 29, and 30.

-IE ci. ci. )( Q) > o

7~-----------------------------------'

6

60

Fig. 28. A, B, C persistence residue curves for ovex residues on and in the rind of Eureka lemons field-treated with 0.75 lb. of a 50 percent wettable powder/lOO gallons, colorimetric residue method (GUNTHER and JEPPSON

1954) (cf. Fig. 22)

From Figure 28 for ovex it was concluded by GUNTHER and JEPPSON

( 1954) that this acaricide migrated very quickly into the cuticular waxes to the extent of about 75 percent loss from the surface within two to three days. The concentration in the wax "layer" reached a maxi-

54 F.A.GUNTHER

3.0----------------------------------------~

, c' A + B + C (sum) 'c , t;

~ t ~ o 1.0 1\ V'} : A ·····I ... ;r .. · .. ·::E .. f .

! y \. "t:: .... :t~-1:..B~~::1~·· .. :E .... ·• ....... .. !/ \ £"--:l:"L A .1 -~---------:..::.::.:::.:.:::. ...... . " --1'"-r-of---"f--r---------':..-.:

00 6 H ~ U W Days

Fig. 29. A, B, C persistence residue curves for dieldrin residues on and in the rind of Eureka lemons field-treated with one lb. of a 50 percent wettable powder/lOO gallons, total organic chloride residue method [GUNTHER and EWART, Unpublished (1955)] (cf. Fig. 13)

E ci. ci.

E o ~

«

1.0

A+B+ C (sum)

O~--~~--~~~~ __ --~-----L ____ ~

o 10 20 30 40 50 60 Days

Fig. 30. A, B, C persistence residue curves for Aramite residues on and in the rind of Eureka lemons field-treated with 40 oz. of an 80 percent emulsive co:ooentrate/l00 gallons, colorimetric residue method [GUNTHER and JEP1"SQN, Unpublished (1950) and GUNTHER et al. 1951] (cf. Fig. 3)

Insecticide residues in citrus fruits 55

Table xm. Some insecticide residues in laboratory-prepared cold-pressed citrus oils from commercial-type treatments a (GUNTHER and coworkers, Unpublished

data over 20-year period)

Range of residues in the oil (p.p.m.) Insecticide

INo. of samples I INo. of samples Lemons Oranges

Aramite 0.1-5.0 3 DDT-type compounds b 7 -294 c 32 17 -82 c 6 Dicofol 0.1-4.0 6 Malathion 4-6 2 3-10 4 Parathion (j 1-23 4 37 -471 6

8-1,600 e, f 10 120 - 2,400 e, g 107 Tetradifon 4-8 10 10-14 3

a At dosages recommended at the time except as otherwise noted. Harvests with the DDT-type compounds and with parathion were made over periods of several years at intervals varying from about 30 to about 90 days after application.

b DDT, DDT-ethylene, and other DDT-decomposition products and congeners as determined by a total organically bound chlorine method.

e From different citrus growing areas in southern California ranging from coastal to desert climates.

(j See also Table XV. Currently recommended dosages are less than those underlying these data (see legend for Fig. 24 and also Table XXVII).

e Highest samples from multiple treatments during the growing season. t Samples at the then-recommended dosages averaged about 25 p.p.m. in the

rind. g Samples at the then-recommended dosages averaged about 300 p.p.m. in the

rind.

mum level within four to five days, then seemed to attain equilibrium proportions as the acaricide traversed this layer possibly in both di­rections. In the meantime, ovex penetrated into the rind, reaching a maximum level within nine to 11 days. These authors (GUNTHER and JEPPSON 1954) concluded that the appearance of the secondary A maxi­mum demonstrated that some of the penetrated materials reissued toward the fruit surface, but that after about 15 days all three types of residue had essentially stabilized in rates and directions of migration. Similar interpretations are applicable to Figures 29 and 30.

The dip in the dieldrin A + B + C curve (Fig. 29) at four days is certainly not real and must reflect the reliability of the residue ana­lytical method employed.

3. Residues in oil. - The interval between application of the in­secticide and the processing of the citrus fruit into cold-pressed oil will markedly influence most insecticide contents of the oil, as abundantly demonstrated in Figures 3 through 26. The limited evidence available

56 F. A. GUNTHER

indicates also that formulations (e.g., wettable powder versus presence of an emulsive oil, Table VI), dosages (Table V), methods of applica­tion (GUNTHER and BLINN 1955, EBELING 1963), maturity of fruits, geographical regions (see DDT, Tables VIII and XIII), and time of year may exert similar influences of varying degrees; varietal differences can also be of quantitative influence (Tables VIII and IX). Typical insecticide residues in cold-pressed lemon and orange oils from washed fruits are collated in Tables XIII and XIV. For comparison, ANDERSON et al. (1963) found 30 p.p.m. of azinphos methyl in Florida orange oil (eight oz. actual/100 gallons, two sprays one month apart, har­vested two weeks after last spray).

Table XIV. Parathion residues in commercially prepared a cold-pressed orange oils from commercial-type treatments in 1949 (GUNTHER and CARMAN, Unpublished)

Orange Insecticide applied Days between Residue in oil application (month) Machine C

variety (lb. actual/IOO gal.) b and harvest (p.p.m.)

Valencia 1 28 (April) F.M. 12 %d 2 (June) F.M. 14

Navel 1 3 (February) F.M. 130 1 3 (March) F.M. 40 1 3 (March) Cit. 450

a With the cooperation of the Research Department, Sunkm Growers, Inc. b From a 25 percent wettable powder. Current recommended dosage, 0.6

Ib./lOO gallons. C F.M. =Food Machinery extractor, Cit. = Citromat extractor. d Plus one quart of emulsive oil.

These data are clearly too limited to be considered representative of residues to be found in unblended 26 oils, for some of the dosages and some of the formulations have changed drastically since these data were collected. They do demonstrate, however, that insecticides can persist from fruit to oil, usually with a concentration effect. The phar­macological significance of these residues is doubtful because citrus oils are consumed per capita in such minute quantities. All of the samples in Table XIII were collected more than 30 days after application; refer­ence to Figures 3 (Aramite), 10 (DDT), 12 (dicofol), 18 (malathion),

26 Citrus oils are commonly blended for optimum aroma, taste, and other normal component variables (e.g., citral) involved in consumer acceptance; stocks from various years are often blended with portions of new stocks to achieve the currently desired properties.

Insecticide residues in citrus fruits 57

24 (parathion), and 26 (tetradifon) will supply the approximate 27 rind residue values underlying these oil residue values.

d) Orange marmalade

Large quantities of citrus rind are converted to marmalade around the world. During manufacture of this product in the United States the rind is thoroughly washed in water, which is discarded, then cooked to about 2220 F. in sugar Syrup.28 Commercial orange mannalade, as the major variety product, was examined over several months in 1952 for parathion contents with results as shown in Table XV.

Table XV. Parathion residues in orange marmalade in 1952 (GuNTHER et al., Unpublished)

Product a

A B C D E F G H

a Various brands from various stores.

Range of residues (p.p.m.)

0.24-0.56 0.50-0.53 0.48-1.34 0.16-0.29

0.18 0.38-0.d3 0.47 -0.67 0.51-0.59

It is highly doubtful if parathion would be detected in these amounts in mannalade today because of its tolerance of one p.p.m. on and in fresh citrus fruits, the currently much less extensive usage of parathion in California citriculture, and the higher dosages that were used in the early days of this versatile insecticide. These data do demonstrate, however, that some insecticides can persist through such drastic treat­ment as mannalade making.29

WISNIEWSKI (1965) reported on the gas chromatographic assays of a domestic and an imported orange marmalade; he found DDT + DDD (TDE) in appreciable amounts in the latter but only questionable

27 The persistence curves involved were established with unwashed fruits, whereas the data in Table XIII are for washed fruits. Rind residue values from the figures should therefore be corrected by the "washing factors" shown in Table XVII.

28 SOUCI and MAmR-HAARLANDER (1966) report three recipes for citrus mar­malades and report on the contents of biphenyl in the final products.

29 See also RAJZMAN (1965), SOUCI and MAmR-HAARLANOER (1966), and STOBW ASSER et al. (1968).

58 F. A. GUNTHER

traces of lindane (and heptachlor?) in the former product. He did not look for parathion.

e) Dried and candied orange rind

Dried orange rind and orange rind "bits" are commercial products used in cake, muffin, and other mixes. These "bits" were picked under a dissecting microscope from samples of the commercial mixes, brushed free of Hour and other particulate additives, finely ground, extracted, and analyzed in 1956 to 1959 with the results for DDT and parathion as shown in Table XVI. Samples of commercial candied orange rind

Table XVI. Insecticide residues in dried (1956-1959) and candied (1954) orange rind (GUNTHER et al., Unpublished)

Insecticide

DDT Parathion

Rind product

Dried Dried Candied Bits b, c

a DiHerent years for repeated values.

Residues a (p.p.m.)

0.8, 1.0, 1.1 0.4, 1.0, 1.3

<0.1 0.3,0.4

b After being baked into muffins, then segregated and analyzed, the residues were diminished by at least half.

a Especially prepared for an orange muffin mix. Removed from a commercial packaged product: 400 g. of mix yielded 80 g. of orange "bits" at least one mm. in diameter.

were also analyzed in 1954 with the result also shown in Table XVI. As in the preceding section (Table XV), today's products should con­tain much lower residues of these two insecticides.

VI. Insecticide residue removal by washing

Commercially sold citrus fruits from this growing area are always washed and gently brushed in warm alkali-soap solution [see sections Vb) 1 and X d) 1 and also Fig. 27] in the packing houses. Extra-sur­face and surface residues should be almost quantitatively removed by this treatment because it also commonly removes up to about 40 per­cent of the natural waxes on the fruits (WILSON 1950), thus requiring the commonly used packing-house waxing operation to replenish this desiccation-delaying protective surface. Because it is possible that some unwashed fruits might be sold in roadside stands or eaten in the or-

Insecticide residues in citrus fruits 59

chards, however, it was ealier felt in our residue evaluation programs that the most meaningful residue values would be those on and in un­washed fruits. Later it was realized that residues both for unwashed and for washed fruits would be meaningful, especially in terms of possibly reducing residues prior to the manufacture of dried citrus pulp cattle feed (see Table XII). The insecticides investigated prior to about 1955 are therefore largely without residue-removal data. Those materials for which such data exist are collated in Table XVII.

In Florida, ANDERSON et al. (1963) found that packing house wash­ing procedures reduced residues of azinphos methyl by about 30 per­cent two weeks after the last application of two treatments one month apart; their data do not disagree with the 80 percent value in Table XVII considering about half their residue was six weeks old by the time it was washed.

These data in toto clearly demonstrate the differences in solubilities in citrus rind oils of the various insecticides included, for those most amenable to removal are obviously those least soluble in the rind waxes and oils. Thus, azinphos methyl, dimethoate, DN-111, malathion, Mo­restan, and tetradifon do not penetrate readily into subsurface regions of citrus rind, whereas Aramite, chlorobenzilate, DDT, dicofol, ovex, and especially parathion penetrate rapidly; carbaryl and ethion seem to be intermediate. DDT, and probably other pesticides as well, reissue in part to the surfaces of treated foliage and fruits after an initial deep penetration (see GUNTHER and BLINN 1955). It is unfortunate there are not more residue-removal data as extensive as those for carbaryl and for the OW-9 compounds (Table XXX).

VII. Systemic insecticides as residues

Although this report is restricted to data on insecticide residues on and in citrus fruits, there is much information on the fate of insecti­cides on and in citrus foliage both in the references cited and in other publications by the same groups of workers. Those readers interested in the penetration, distribution, metabolic pathways, and rates of loss of pesticides on and in citrus foliage will find a wealth of information in these publications [see also section XI e) ].

METCALF et al. (1954 a and b, 1955, and 1957) sprayed a mature Valencia orange tree (mature fruits) and a Eureka lemon tree (green fruits) to the run-off point with an aqueous demeton-isomer solution containing P32-labeled O,o-diethyl 5-2-( diethylamino) ethyl phosphoro­thiolate (thiol-isomer base), or demeton thiol isomer at the rate of 40 g.j100 gallons of water, a dosage considered suitable for commercial practice. Replicates of ten fruits were picked from each tree at the intervals indicated in Table XVIII. The surface contamination was de-

60 F. A. GUNTHER

Table xvn. Insecticide residue removal from field-treated citrus fruits by washing­brushing a procedures 14 to 37 days after field applications of the then-recom­

mended dosages and formulations

Insecticide

Aramite

Azinphos methyl

Bidrin

Carbaryl

Chlordane

Chlorobenzilate

DDT

Dicofol

D D

imethoate N-lll

E thion

alathion

orestan

M

M o mite

o vex

o P

W -9 Compounds e

arathion

T etradifon

Citrus Days after variety treatment

Lemons 20 Oranges 20 Lemons 19 Oranges 14 Oranges 14

Oranges 8 Oranges 26 Oranges 60 Lemons 27

Lemons 14

Lemons 2 Lemons 86 Oranges 2 Oranges 86 Oranges 7

Oranges 31-37 Oranges 14 Oranges 30 Oranges 7 Oranges 30 Oranges 8

Oranges 26 Oranges 30

Lemons 30 Oranges 30 Oranges 2 Lemons 2 Oranges 2 Lemons 33

Residue removed b Reference C

(%)

Traces GUNTHER et al. (1951) Traces

- 60 GUNTHER & CARMAN, - 80 Unpublished ( 1963) - 40 GUNTHER & EWART, Unpublished ( 1964) - 85 GUNTHER et al. (1962 a)

- 40 Traces

15 GUNTHER & CARMAN, Unpublished (1955) - 25 GUNTHER & JEPPSON, Unpublished ( 1954) - 65 GUNTHER et al. (1950)

Traces GUNTHER et al. (1946)

- 70 GUNTHER et al. (1950) Traces GUNTHER et al. (1946)

- 30 GUNTHER & JEPPSON, Unpublished ( 1956) - 30 d GUNTHER et al. (1965)

- 75 GUNTHER & CARMAN, - 30 Unpublished (l966) - 75 GUNTHER et al. (1962 b) Traces -100 GUNTHER & CARMAN,

Unpublished ( 1959) - 70 GASTON et al. (1968) - 40 GUNTHER & JEPPSON, Unpublished (1967)

Traces GUNTHER & JEPPSON Traces (1954) - 20 JEPPSON et al. (1968) Traces GUNTHER et al. (1950) Traces - 60 BLINN et al. (1959)

a In warm detergent, mild soap solution, or 50 percent soap - 50 percent sodium carbonate solution.

b "Traces" means only a few percent apparent removal; the washings were not analyzed.

C The references to the published literature contain the actual residue values. d Highly variable, as confirmed subsequently by GUNTHER and BARKLEY [Un­

published (1965)]. e See Table XXX.

Insecticide residues in citrus fruits 61

Table XVIII. Residues of demeton thiol-isomer equivalent in orange and lemon fruits after being sprayed with 40 g./IOO gaUons (METCALF et al. 1957)

Residue (p.p.m.)

Interval after Oranges Lemons

treatment

Surface Rind Pulp Surface Rind

1 hour 0.28 - - 0.23 -3 days 0.15 0.063 0.00 0.22 0.24 7 days 0.32 - 0.00 0.38 0.21

14 days 0.15 0.08 0.00 0.21 0.32 - 0.06 a - - 0.34 a

28 days 0.03 0.06 0.00 0.04 0.24 - 0.05 a - - 0.30 a

a Values obtained by enzymatic (anticholinesterase) assay.

:! ';: " c 2 .. e ..

0

10

5

1

0.5

CzHsO, sea) ,r-o (S)-cz"-4-S-CzHs

CzHsO

\ , \ \ \ \ , \ , \

\ Orange iuice ... , , \ \ ,

\ , , , , \ , .

\, Thiono-isomer

\ , , , \ \

0.1 0~-....IIO--2.1.0---'3L..O ....... "-:'40::---!50-

Days

Pulp

-0.00 0.00 0.00 -

0.00 -

Fig. 31. Persistence curves for the thiol- and thiono-isomers of demeton equiva­lent in Valencia orange juice (replotted from METCALF et al. 1955). Demeton "units" are chlorofonn/water partition coefficients of the extractives

62 F. A. GUNTHER

termined by laving the fruits with acetone or with water containing 0.1 percent of the surfactant Triton X-100 and radio-assaying aliquots of the combined lavings. The washed fruits were carefully peeled to avoid contamination of the pulp and the rind and pulp were assayed separately. Analytical values for the demeton equivalent are given in Table XVIII and show that residues in the pulp of both fruits were below the limits of detection of either the radioassay or the cholinester­ase assay methods. The green lemon fruits, which were considerably smaller than the oranges, contained consistently higher residues than the ripe Valencia oranges and, interestingly, this insecticide penetrated readily into the rind of the lemons but not of the oranges. If acetone was the laving solvent for the lemons, it probably carried some of the insecticide into the rind.

The half-lives of the thiol- and thiono-isomers in orange juice were found (METCALF et al. 1955) to be about 30 and 20 days, respectively, as determined by the partition coefficients between chloroform and water. The active isomers partition about 98 percent into the chloro­form phase while the inactive metabolites partition about 98 percent into the water phase. Persistence curves for the thiol- and thiono-iso­mers in the orange juice are reproduced in Figure 31 (METCALF et al. 1955); half-lives for both isomers are about four days as deduced from this figure, in contrast to the values cited above.

The behavior of octamethylpyrophosphoramide (schradan) in citrus plants had earlier been investigated by METCALF and MARCH ( 1952), again using P32-labeled compound. Applications of schradan to Eureka lemon and Valencia orange fruits were absorbed more rapidly into the rind than into the leaves, and penetration into the pulp oc­curred. The maximum concentrations of schradan and phosphorus­containing metabolites in both juices were about 0.03 p.p.m. from the application of a 0.036 percent aqueous solution, after 18 days and 0.42 p.p.m. 43 days after application of a 0.1 percent aqueous solution for lemons and 0.58 p.p.m. after 50 days for oranges. Figure 32 shows graphically the residues present in the lemons and oranges (two fruits/ analysis) for a period of 57 days after application of the 0.1 percent aqueous solution. The half-life of this compound in citrus rind is obvi­ously greater than 57 days, unless the P-containing metabolites repre­sented the major count in the assay utilized.

ATKINS et al. (1961) analyzed single mature Valencia oranges sprayed with mevinphos (Phosdrin) over a period of 14 days after treatment. Initial deposits were reduced to about one-third during the first 24 hours, indicating a half-life of less than one day. Table XIX gives the residue data from three different levels of treatment, on the whole-fruit basis.

Insecticide residues in citrus fruits

e Ii 2 ~ 1.0 c ~ 0.8 a ~ 0.6

'" 0.4

0.3

Juice !', . , : \ Oranges . ' J \ . "

.' /./ ....... .." 0.2

0.1 o~--'''"':':' --2-:':~:---~30::---""4'::'0---:5-!:.'0:----::'6~'

Days

63

Fig. 32. Persistence curves for schradan equivalent in the rind and in the juice of Eureka lemons and Valencia oranges. Dosage: 0.1 percent aqueous solu­tion containing 0.04 percent surfactant applied directly onto fruits (MET­CALF and MARCH 1952)

Table XIX. Residues of mevinphos in whole Valencia oranges (ATKINS et al, 1961)

"Picked when fruit had dried (abollt four hours).

64 F. A. GUNTHER

VIII. Some market survey insecticide residue data

There have been two interconnected, long-term nongovernmental surveys of insecticide residues in marketed citrus fruits, both under the auspices of the California-Arizona Citrus Industry through the Cali­fornia-Arizona Citrus League.3o The first part of this program, with FAS PL-480 support,31 involves establishing and evaluating pesticide residues in citrus fruits (and other crops) as received on the French market. Except for some lemons produced on the French Riviera and some oranges from Corsica, most citrus fruits sold in France are im­ported from several countries, including the California-Arizona citrus producing areas. The second program is also under the California­Arizona Citrus League, and is concerned only with citrus fruits pro­duced and sampled in the California-Arizona citrus areas.

a) The French program

About 35 insecticides are looked for in the French program. Those insecticides of interest to California-Arizona citriculture (see Table I) are relisted from the French program in Table XX with the claimed minimum detectabilities and laboratory recoveries in the presence of citrus fruit extractives; endosulfan, endrin, fenitrothion, and toxaphene are also listed for the guidance of interested readers even though they are not in the California recommendations (see Table XXII). This French listing does not include Aramite, azinphos methyl, Bidrin, car­baryl, demeton, dimethoate, dioxathion, the DN-compounds, EPN, mevinphos, naled, Neotran, or phosphamidon, insecticides which are listed in Table I as having been or currently of interest to the Cali­fornia industry. Among these, azinphos methyl, dimethoate, mevin­phos, naled, and phosphamidon can be determined by other proce­dures, according to MESTRES (1968 and Unpublished).

Results on California-Arizona citrus fruits as received in Europe will be extremely valuable in supporting the parallel activity described in the next subsection.

b) The California-Arizona Citrus League program 32

30 As guided and interpreted by Dr. Lloyd W. Hazleton, under contract with the Navel Orange, Valencia Orange, and Lemon Administrative Committees, with earlier analytical work on domestic samples by Hazleton Laboratories, Inc., Falls Church, Virginia, and later by Terminal Laboratories, Los Angeles, California.

31 Under Professor Robert Mestres, University of Montpellier, France. FAS = Foreign Agriculture Service of the U.S. Department of Agriculture.

32 The residue data utilized in this subsection are reproduced with the per­mission of the California-Arizona Citrus League. See also HAZLETON (1968) for a more detailed discussion of this program.

Insecticide residues in citrus fruits 65

Table XX. Insecticides looked for as possible citrus residues in the French program (MEsTREs 1968 and Unpublished)

Minimum amount claimed detectable Claimed

Insecticide recovery

Nanograms" I p.p.m.b I (%)

Aldrin 0.05 0.002 81 BHC 0.05 0.002 94 Carbophenothion 1 0.03 94 Chlordane 0.4 0.02 75 Chlorobenzilate 4 0.1 63 DDEc 0.1 0.005 -DDT 0.2 0.01 94 Diazinon 2 0.05 80 Dicofol 0.2 0.005 66 Dieldrin 0.1 0.002 80 Dinocap 4 0.1 -Endosulfan d 0.4-1.3 0.01-0.04 90 Endrin 0.1 0.002 65 Ethion 0.5 0.01 60 Fenitrothion 0.1 0.002 85 Heptachlor 0.2 0.01 90 Heptachlor epoxide 0.2 0.01 90 Lindane 0.05 0.002 87 Malathion 1 0.03 60 Methoxychlor 1 0.03 80 Methyl parathion 0.3 0.01 80 Parathion 1 0.03 80 TDE(DDD) 0.1 0.005 73 Tetradifon 1 0.03 85 Toxaphene 0.4 0.02 75

"By gas chromatographic techniques under very carefully controlled condi­tions, minimum 10 percent scale deflection.

b After an injection of four microliters of chromatographically fractionated ex­tract, representing 50 g. of whole fruit, concentrated to 5.0 mI. in most instances.

c A decomposition (also metabolic) product of DDT. of Two isomers.

In a continuing "quality assurance" program, directed at the post­packinghouse level of fruit, the California-Arizona Citrus Industry is endeavoring to achieve a "continuous view of the pesticide and other additive residues on their fruit at the time they are offered in interstate commerce or for delivery to foreign markets" (Hazleton LaboratOries, Inc. 1967). The basic concept of this farsighted program is that the in­dustry should attempt to provide adequate and complete pesticide application data for all its groves, and if this information is properly correlated with a minimal yet adequate continuing residue analytical monitoring and surveillance activity, the industry will- at any given

66 F. A. GUNTHER

time for any given variety of citrus fruits or for any given producing area - have reliable information about the pesticide residue burden of the fruits involved. The significance of the residue levels found for par­ticular pesticides, unless above tolerance limits, cannot be ascertained until enough data are available to establish trends and patterns of oc­currence, but certain indicated patterns have already emerged and some tentative conclusions are justified, as discussed below.

Initially, this program involved specific sampling and residue assay of selected lots of southern California and of Arizona fruits to identify and define the profile of pesticide residues present and the develop­ment of an information system on pesticide applications by the growers in the entire area. With this information, a fruit sampling and analyti­cal monitoring program was established for both California and Ari­zona. As data accumulated, residue profile predictions were attempted so as to permit the directed acquisition (surveillance sampling) of gap­filling residue data as the program continued. The objective here was to establish the minimum adequate monitoring program to maintain assurances of freedom from illegal residues or amounts of residues. Both random and directed sampling programs were necessary to per­mit the desired evaluations of patterns and magnitudes of residues in the approximately 600 samples analyzed for 28 pesticides through 1967.

The observed residue data for insecticides only on and in citrus fruits 33 are reproduced in Table XXI; reference to Table I will allow comparisons of residues with tolerances.

These data do not distinguish either varieties of fruit or areas of production. Analysis of the detailed data underlying this summary table have permitted certain observations and conclusions (Hazleton Laboratories, Inc. 1967), however:

1. There are very significant differences between producing areas as far as pesticide residues are concerned. Desert fruit displays the least complicated profile, has lower probability of incidence, and has significantly lower average and maximum magnitudes of residues.

2. DDT and dicofol are the most consistently present residues, except in fruit from Phoenix, Arizona, where DDT alone is the expected profile.

3. In terms of absolute magnitude, dicofol is undisputably the leader with dioxathion second.

4. There were discernable trends in the pesticide usage from 1964 to 1967. For example, parathion residue incidences are decreaSing, but those of dieldrin are increasing.

5. Field intelligence, i.e., data on pesticides applied or probably ap-

33 Without regard to variety.

In3ecticide residues in citrus fruits 67

Table XXI. Residues found in California-Arizona citrus crops from the market monitoring program through 1967 (Hazleton Laboratories, Inc. 1967)

Insecticide

Aramite Carbaryl Chlordane Chlorobenzilate DDEc DDT Diazinon Dicofol Dieldrin Dioxathion Endosulfan Endrin Ethion Heptachlor' Heptachlor epoxide Lindane Malathion Methyl parathion Ovex Parathion Phosphamidon TDE(DDD) Tetradifon Toxaphene

No. of samples

Tested a

77, -, -3,-, -

79, -, -88, -, -91, 88, 346

170, 88, 346 -,-, ?

167, 68, 346 171, 88, ?

6, 75, 346 , , ?

92, -, --,88, ?

170, 88, -91,88, -

135, -, -167, 88, 346 -,88, --,-, ?

171, 88, 346 -,9, -91, 88, 346

128, -, 346 -, -, 346

I With positive results a

0,-,-3,-,-0,-,-5,-,-

15, 53, 2 88, 65, 81 -, -, 1 72, 22, 48 2,26, 1 0, 18, 3 -,-, 1 0,-,­

-, 4, 1 26, 0,-0, 0,-

15, -,-11, 36, 5 -,3,--,-, 1 48, 6, 4 -,4,-16, 16, 9 9, -, 26 -,-,2

a Series numbers are results from different laboratories. /) Based on whole fruit. e A decomposition (also metabolic) product of DDT. d Despite its nonuse in California citriculture . • Apparent.

Maximum residue found (p.p.m.) a, b

- - -, , 0.2, -, -- - -, , 1.9, - , -0.04, 0.02, 0.1 0.6, 1.0, 1.0

, -, 0.3 1.9, 2.1, 3.0 0.005, 0.02, 0.1 - , 1.7, 2.6 - , - , 0.2 d

- , - , -- , 0.04, 0.1 0.02, - , -- - -, ,

0.01, -, -0.2, 0.3, 0.5 -, 0.2, --, 0.02, -0.22, 0.27, 0.7 -, 0.03, -0.28, 1.1, 0.7 0.3, - , 0.3 - , - , 1.1

plied (surveillance), appears to be an important input to a residue­testing program. It is believed that such "before the fact" hypothesis may improve testing efficiency by as much as 50 percent.

6. As a corollary to item 5, it is important to note that if any pesticide residue is detected at the rind level, then it is very highly probable that more than one pesticide is present.

7. Also, if DDT, dicofol, or dieldrin are not detected at the rind level, then it is probable that no other pesticide residue will be detected.34

34 The durability of this broad statement about "pesticides" is questioned by this reviewer.

68 F.A.GUNTRER

8. A sampling and monitoring program to provide profile statistics and to identify trends is practical. It would appear desirable, however, to obtain detailed research-type analytical data since the essentially "censored" samples of a regulatory agency have an extremely poor prediction content.

9. The ability to correlate application data with expected residue profile requires further investigation. Based upon the program data obtained to date, it should be possible to develop a prediction model which could more explicitly indicate where and when to sample and what to test for.

The data in Table XXI must be interpreted with caution, for not all of the three laboratories involved always tested fruits from the same lots or even from the same growing areas. Also, some of the samples were directed or surveillance samples, i.e., they were selected based upon prior knowledge of insecticide applications in certain areas. With these reservations in mind, certain conclusions about area effects are possible, according to Hazleton Laboratories, Inc. (1967) (essentially quoted):

1. Phoenix, Arizona. In the last year, 1966-67, two of the laboratories tested 36 samples of citrus fruit produced in this· area. The residue profile is centered around the DDT-TDE-DDE pesticides. The magnitudes range around 0.01 p.p.m. on a whole-fruit basis. Mala­thion and dieldrin were detected on samples selected in March or later at magnitudes generally below 0.01 p.p.m. on the whole-fruit basis. In light of the program to date, fruit produced in the Phoenix area has the least complicated residue profile and the magnitude of residue, when detected, is significantly less than that observed from other producing areas. No instance of the presence of dicofol has as yet been reported for Phoenix, Arizona fruit.

2. Yuma, Arizona. Citrus produced in the Yuma area was also sam­pled and tested in the 1966-67 program year. The residue profile is similar to that of the Phoenix area with the major differences that dicofol was detected in about 25 percent of the 31 samples at below 0.1 p.p.m. on a whole-fruit basis. The DDT-TDE-DDE complex appears in a fairly consistent pattern with the combined maximum approaching 0.3 p.p.m. on the whole-fruit basis. This is significantly higher than Phoenix fruit but appears correlated to time, with the maximum observations decreasing in going from winter to summer. The malathion and dieldrin profile is again possibly a time function since they were observed only on spring fruit.

3. California. The testing of California-produced citrus during 1966-67 was divided among the three participating laboratories, with both

Insecticide residues in citrus fruits 69

random and selected samples. The following general observations may be derived from the data reported: (a) The DDT-TDE-DDE complex is the most consistently observed

residue. Average magnitudes for California fruit remain below one p.p.m. on a whole-fruit basis but occasional observations to two p.p.m. must be anticipated.

(b) Dicofol retains its significantly high ratio of incidence and magnitude. There is surprisingly good agreement among the laboratories on the average and maximum magnitudes for this chemical, 0.5 to 0.7 p.p.m. average and 4.0 p.p.m. maximum.

(c) Dioxathion and chlorobenzilate were two pesticides for which little data were available prior to the 1966-1967 program. While the probability of their presence is much less than that of DDT and dieofol, the 1966-1967 testing suggests that their average and peak magnitudes, when present, are as significant as those of dicofol.

(d) The incidence of dieldrin, in all varieties for the southern Cali­fornia area, remains as a consistently high probability of pres­ence at the rind level.

This quality assurance program is being continued.

IX. Multiple residue methods for citrus fruits

As the results of increasing numbers of more effective and some­times more toxic pesticides, metabolite considerations, lowering mini­mum detectability requirements, instrumental vagaries (WESTLAKE

and GUNTHER 1967), multiple residues, and complexities of reliable residue analyses, the U.S. Food and Drug Administration recently has also been promoting the use of two or more residue analytical methods in residue-data development programs involving foodstuffs. Multiple methods are especially important if the pesticide is highly toxic to warm-blooded animals and/or is known to metabolize or is suspect of metabolizing from strongly sloping persistence curves. For incisive in­formation, the methods clearly should respond to different parts of the parent molecule as, for example, gas chromatography for intact para­thion or paraoxon, associated with a colorimetric method for reduced ("amino") parathion or paraoxon. If the insecticide contains organi­cally bound halogens, as in about 40 percent of the modern pesticides, a total halogen method associated with a more specific method can provide unusually useful residue data. Thus, if the organohalogen value 3~ interpreted in terms of the parent insecticide is larger than the

85 Extractives in solution in a water-imiscible solvent are washed thoroughly with distilled water, 10 percent nitric acid solution, and distilled water to remove inorganic halides dissolved or entrained in the original extractives solution as well as the catholic and interferingly organic-solvent-soluble quaternary halide salts of phosphatidyl cholines (lecithms) in plant extractives (GUNTHER et al. 1966).

70 F. A. GUNTHER

more specific value for the parent compound by the other method ( s ), degradation to halogen-containing persisting metabolic or other prod­ucts is indicated; if the two (or more) values for a given sample agree, it may be concluded that the sample is free from halogen-containing alteration products. Clearly, the companion "specific" method by its total chemistry must ideally respond only to the intact parent molecule if this dual analytical system is to be of maximum utility.

An example of the utility of this concept in citrus residue investiga­tions is afforded by the acaricide dicofol, the residues from which were analyzed by three methods each responding to different parts of the parent molecule (Fig. 12). The "chloroform method" responded to the trichloromethyl group by a strongly alkaline modified Fujiwara reac­tion, the "ketone method" determined by ultraviolet assay the 4,4'-di­chlorobenzophenone moiety as released by mild alkali and oxidation, and the total organically bound chlorine method responded to the five chlorine atoms in dicofol released as chloride ion by oxidative com­bustion (GUNTHER and BLINN 1955). These curves with their identical slopes demonstrate clearly the unusually long persistence of this acari­cide in citrus rind and its stability in situ. The parallelism of the three persistence curves demonstrates that the intact molecule persists with slight if any change: if, with time, the ketone had formed the slopes of both the colorimetric and the total organic chloride curves would have increased negative slopes in comparison to the slope of the ketone curve. The probable presence of a chlorine-containing contaminant in constant proportion to the parent compound is also indicated. Half­lives by the three methods are 189, 188, and 197 days, respectively.

Similarly, the persistence curves for carbophenothion (Fig. 7) were obtained by the total organic chloride method plus a more specific method, for chlorobenzilate (Fig. 9) by both colorimetric and ultra­violet methods, and for tetradifon (Fig. 26) by colorimetric, infrared, and total organic chloride methods.

Not just any combination of detection methods will serve the most useful purposes, however.

For example, the carbophenothion residues in lemon rind (Fig. 7) demonstrate that this acaricide is altered appreciably in aging residues to one or more strongly persistent chlorine-containing fragments or other products that are not segregated by the isolation procedure or else do not respond to the p-chlorothiophenol test utilized. The total organic chloride procedure did not involve chromatographic segrega­tive steps and thus responds to the chlorophenyl moiety regardless of any in situ alterations to the rest of the molecule. The total organic chloride residues also fall off with time, but at a slower rate: the half­lives for the organochlorine-responding species and for the parent molecule are 62 and 20 days, respectively. By analogy with other pesti-

Insecticide residues in citrus fruits 71

cldes, a proportion of this changed product could be a sulfone deriva­tive, a possibility which should have been checked by infrared assay (e.g., see Fig. 26). These curves and the chemistry involved in their establishment are of the type that could be of maximum value to regu­latory officials.

In contrast, the curves for chlorobenzilate residues in lemon rind (Fig. 9) are of little value in establishing the probable presence of stable chlorine-containing or any other metabolites in aging residues. Both analytical procedures used involved hydrolyzing the parent acari­cide to p,p'-dichlorobenzilic acid, which was then oxidized to p,p'­dichlorobenzophenone, an aromatic compound readily determinable by both colorimetric and ultraviolet absorption methods. The total analytical procedure conferred considerable specificity to the determi­nations, but both final measurements involved the same species; these two mutually nondiscriminatory measurements did buttress each other, however. With a half-life of about 28 days, and again by analogy, this disappearing acaricide is undoubtedly forming at least some reason­ably stable chlorine-containing alteration products. The total organic chloride procedure should have been companion to either of the methods utilized in this program.

Thus, the tetradifon residue program with lemon rind (Fig. 26) provides maximum information to regulatory officials. With the total organic chloride method as "detective," the infrared procedure for the diphenyl sulfone moiety and the colorimetric procedure (polynitrated aromatic moiety in strongly alkaline solution) buttress each other with reference to unchanged tetradifon, yet it would seem either that a non­tetradifon responding alteration product slowly builds up or that a major chlorine-containing impurity in the formulation used is more stable than the major active ingredient. Half-lives for this acaricide from these curves are 120 days for the total organic chloride compo­nent( s), 82 days for the sulfone, and 92 days for the aromatic-group component ( s). If the infrared assay at 42 days had been lower, the infrared and colorimetric curves would have been parallel, as expected.

A total sulfur method can also be used as a "detective" method, as was illustrated in the residue persistence curves of Figure 21 for Omite in orange rind. The upper curve represents the organosulfur compo­nent of the single gas chromatographic peak obtained, and the lower curve represents the response of the single peak (from a different column) to the hydrogen-Hame detector. Unless there were gas chro­matographic decomposition, the two lines should be parallel and co­incident, but there were not enough points accurately to establish the lower line. These curves do establish that the peak measured by hydro­gen-Hame detection also contained approximately the correct propor­tion of organic sulfur to correspond to the empirical formula and gas

72 F. A. GUNTHER

chromatographic characteristics of unchanged Omite, but they do not establish that the disappearing portion of the Omite (contaminant?) still contains the sulfur atom. The half~life of Omite is about 60 days and it does metabolize or otherwise lose its identity with time, but the nontransient products do not readily gas chromatograph.

These four figures clearly demonstrate the basic desirability of using an adjunct method, such as the organochlorine, organosulfur, or the new organonitrogen methods, on extractives that have not been rigor~ ously cleaned up. If the final multiple detection methods are applied to aliquots of the same cleaned up 36 solution of extractives, they can only buttress each other in terms of the species isolated, as in a gas chromatographic peak from a single column.

An excellent example of the information that can be derived from the use of several carefully chosen multiple residue analytical methods is illustrated with the acaricide~insecticide~fungicide Morestan, as dia~ grammed in Figure 33. Five mutually buttressing residue methods

r-----.--GLC=r-c-~(X:x)~[(x:x:l·· ELECTRON -CAPl'VRE

DE'l1!:CTOR

oc:) RING BACKBONE

IIICROCoIJLOMETRIC DETECTOR

2SATOMS

MORESTAN 1 • NI<NIIaII+

'I1IIN - LAYER CHROMATOGRAPHY

N 8

CHIy.7y ~ 'NIINIIa)

~~/ I a9CILLOPOLAROGRAPIIY :C-O FUNCTION -0.94 to -1.011 voila

FLUOROMETRY

INTACT MOLECULE Exc. A ooo .. ~ Em. )'38011j&

N 8

REO COLOR BODY Aa ... 610 .. ,.

ELECTROLYTIC CONDUC1lVITY DETECTOR

2 N ATOMS

Fig. 33. Illustrative incisive residue analytical scheme for Morestan in citrus fruit extratives (GASTON et al. 1969). Nitrogen detection added by present author

were used in this preregistration evaluation of Morestan residues on and in Eureka lemons and Valencia oranges. At the time, the nitrogen~ specific electrolytic conductivity detector was not available, but it (or an equivalent) should be incorporated into any "total fate" program

36 As illustrated by Figure 21, properly applied gas chromatography can rep~ resent segregation and thus rigorous cleanup, probably its most useful application (WESTLAKE and GUNTHER 1967). The rest of the gas chromatogram then becomes of major importance in interpretation of alterations of the parent molecule.

Insecticide residues in citrus fruits 73

involving nitrogen-containing parent compounds to help characterize both the parent molecule and its in situ alteration products. Conclu­sions drawn from this application (GASTON et al. 1969) were that there were no statistical differences among the five residue half-life values obtained for both lemons and oranges (see Table VII), and that initial deposits by extrapolation (e.g., Fig. 19) were in good agreement. Fur­ther, the residues measured were characterized as unchanged Morestan by four interwoven and independent ways: correct GLC retention time, correct polarographic reduction potential, correct fluorescence spec­trum, and correct Rt on thin-layer chromatography; quantitation was achieved by five of the six methods in Figure 33 (nitrogen detector excluded).

In addition to these general qualitative identifications, each quanti­tative method was specific for individual functional groups or sulfur. A polarographic reduction potential of - 1.0 volt (vs. an amalgamated silver wire) is in the region where other conjugated carbonyl groups reduce and the polarographic reduction equivalent weight of Morestan was found to be 115, which corresponds to two electrons per molecule; thus, it was highly probable that it was the carbonyl group that was being reduced. The microcoulometric titration detector was specific for sulfur (as sulfur dioxide in the combustion products) which could come only from the dithiocarbonate group. The colorimetric method responded to the 6-methyl-2,3-quinoxaline-dithiol present before and after hydrolysis. These three methods accounted for all the parts of the Morestan molecule. Capture of a thermal electron probably involved placing an electron either in a low-lying antibonding orbital or in a nonbonding orbital which is a property of the bonding molecular pi­orbital electron system and thus is a function of the whole molecule. The fluorometry as used probably involved the excitation of a high energy bonding pi-electron and its subsequent radiation of energy and thus was also a function of the whole molecule.

The agreement between the five methods applied to Valencia oranges was remarkably good. Calculated initial deposits by all methods were proportional to the amount of material applied indicating that the application, sampling, and analytical procedures were all equally good. The average half-life of Morestan on Valencia oranges was 36 ± 8 days and was independent of the dosage within the dosage range studied, a relationship previously established for many insecticides on and in citrus fruits (see Tables IV, V, and VI).

Choices and numbers of methods required to support both charac­terizations of residues measured and their quantitation depend upon the structure and obvious chemistry of the parent molecule, the par­tition efficiency and the chemistry of the isolative and cleanup opera­tions utilized, and the biological activities of aged residues vs. parent materials.

74 F.A.G'ONTHER

x. Developmental citrus residue-analytical methodology with fresh fruits

This section is included because the preparation of citrus rind and pulp extractives representative of the field treatment has evolved em­pirically and involves some highly special techniques and analytical considerations not ordinarily encountered with other fresh substrates. Inclusion of this material makes tins review self-sufficient for analysts interested in working with citrus fruits in residue developmental, sur­veillance, and monitoring programs.3T

Some of the details in this section have not previously been pub­lished.

a) Presampling considerations

All the tree-fruit presampling considerations discussed in detail by GUNTHER and BLINN (1955), GUNTHER (1962), GARBER (1963), L YKKEN

(1963), and VAN MIDDELEM (1963 and 1968) apply to citrus fruits. They should be studied carefully before any residue investigation in­volving fruits is undertaken.

"The belated decision to secure residue data from an experiment already in progress and designed originally for the accrual of biological performance data may well yield misinformation of the most appalling sort" (GUNTHER and BLINN 1955). Residue data can be no better than the adequacy of the sample to reRect the sought relationship. Before field samples are collected the residue analyst should have as much detailed quantitative information as possible on the following factors:

1. Pretreatment history of the trees involved and the actual analytical background contribution from fruits from those trees before the new treatment. If the background is too high to be compensated (GUNTHER 1962) or too variable, other groves should be investi­gated; ordinarily, residue values 2 x the background variation are acceptable, but some authorities insist upon minimum 4 x for sig­nificance (GUNTHER 1962). Some of the normal components of

87 Because of the importance of residue evaluations of dried citrus pulp cattle feed prepared from pesticide-treated fruits, detailed procedures for its laboratory­scale preparation were included in an earlier section [section Vb) 1]; it is sub­sampled by quarters and stripped by techniques suitable for any granular porous material which yields large amounts of soft waxy extractives. It is cleaned up and analyzed by the same procedure as used for citrus rind samples. Final residue data are corrected back to zero moisture content or sometimes to 10 percent moisture content of parent sample (DEAN-STARS: procedure by codistillation with benzene or toluene).

Insecticide residues in citrus fruits 75

citrus fruits may contribute significant and often highly variable background to a particular determinative method for either parent compound or alteration products. If so, another total method must be found. Contributions from previous interfering pesticide treat­ments - unless recent - will probably be sufficiently uniform as per­sisting residues to be statistically compensatable. These considera­tions are collectively designated as the "analytical integrity" of the true control samples: that is, representative samples of the crop before treatment, as contrasted with companion control samples from nearby untreated trees and collected at each sampling interval.

2. Availability of periodic and acceptably "clean" control samples from nearby untreated trees, upwind from the treated trees, throughout the duration of the experiment.

3. Both control and treated fruits must be of the same variety and of the same age or degree of maturity. If the fruits to be used are not fully sized, growth-dilution factors must be incorporated into the final residue data and their interpretations. Fortunately, citrus fruits attain essentially maximum volume about 60 days prior to earliest harvest based upon acceptable quality, and a large per­centage of the crop will remain on the trees at least 60 days after normal harvest time. This behavior means that the residue analyst can construct persistence curves over a 90- to 120-day interval without the necessity for growth-dilution compensations.

4. The type of analytical value sought will markedly influence both treatment and sampling techniques. For example, atypical deposits and residues may be associated with the last quarter of the tank of spray mixture 38 and with fruits below the mid-belt around the circumference of the tree but especially on the shaded side; me­chanical full-coverage applications probably give more uniform (reproducible) deposits than manual applications [CARMAN et aI., Unpublished (1966)]. Average deposits and residues are most realistically obtained from fruits from the outside of the entire mid­belts of trees sprayed from the middle two quarters of the spray tank.

5. The analytical integrities of the treated and control trees must be maintained during the entire period of the experiment.

6. There must be sufficient fruits on the treated and control trees to allow for adequately sized samples for the entire program, includ­ing the oversize samples required for the preparation of both con­trol and treated dried citrus pulp cattle feed [see section Vb)].

88 From inadequacy of agitation, Hocculation, flotation of some of the spray ingredients, and other factors.

76 F. A. GUNTHER

Failure to accommodate any of these considerations may result in meaningless residue data.

b) Sampling procedure

The design of the citrus fruit sampling procedure is contingent upon many factors in addition to those mentioned in the preceding subsection. These additional factors 89 include:

1. Analytically establishing initial deposits on citrus fruits is very difficult by direct analysis of immediate posttreatment samples (see footnote 14 for elaboration); rather, initial deposits are more satis­factorily established by extrapolations of sufficiently detailed de­gradation curves, as earlier discussed in detail. Some formulations (e.g., emulsive concentrates) of some insecticides deposit more heavily on lemons than on oranges, but sometimes the converse is true, as also discussed earlier. In general, most formulations of most insecticides and acaricides at from about 0.25 to 2.0 Ib./100 gallons and from 250 to 2,500 gallons/acre afford initial deposits between about one and about 20 p.p.m. on a rind basis (see Figs. 3 through 26, Tables IV and V).

2. From biological performance data it is usually possible to predict an adequately approximate effective deposit half-life so that a sampling schedule can be arranged; for example, an insecticide providing short-term control normally would involve closer sampl­ing intervals than one providing long-term control. Nonetheless, as illustrated in Figures 3 through 26 degradation half-lives are al­ways shorter than persistence half-lives so that the initial samplings for degradation curves should be at shorter intervals than later samplings when the deposits have become residues. A standard sampling sequence is at about 3, 7, 12, 19, 26, 40, 54, 82, and 106 days to allow normally for three or four points for the degradation curve and five or six points for the persistence curve. Samples for conversioB to dried citrus pulp cattle feed are normally collected 20 to 40 days after the spray application. For short-lived materials [e.g., Aramite (Fig. 3), Bidrin (Fig. 5), chlordane (Fig. 8), and diazinon (Fig. 11)], sampling intervals should be more frequent.

3. The duration of the sampling program will also be dictated in part by the limiting detectability of the residue analytical method in the presence of the substrate extractives. Clearly, as the residues approach this limit there is no value in continuing with additional, later samples.

89 See references in subsection a) of this section for detailed discussions of sampling considerations and procedures for crops in general.

Insecticide residues in citrus fruits 77

4. With most insecticides, rain within about three weeks after the spray application requires repetition of the experiment because of probable serious losses of deposits and effective residues (viz., Table XVII).

It has been well-established in the present program that 32 fully­sized citrus fruits per sample, replicated at least twice, constitute an adequately reproducible field sample when ultimate credibility of residue data rests upon a degradation or persistence curve. If such curves are not established, statistically satisfactory residue data re­quire at least 64 fruits/sample replicated three times at any period at least three days after treatment [CARMAN and GUNTHER, Unpublished (1950 and 1955)]. Samples of individual lemons and oranges with several insecticides have shown extreme variations in effective resi­dues, apparently largely dependent upon location of the fruit on the tree; some of these variations have been ten-fold in magnitude from fruit to fruit from opposite "sides" of the tree or from top to bottom of the tree (GUNTHER and BLINN 1955). Samples of fruits less than fully sized may require correspondingly larger numbers of fruits/sample. The manner of collection of any of these samples determines whether the sample is to be representative of the mean deposit or residue load resulting from the treatment or to establish a range of values. The following procedure was designed to achieve this former objective:

The minimum plot should contain at least 16 normal mature trees, preferably in a row. Mter being sprayed from the middle portion of the tank contents, the center eight trees are tagged for sampling. Two samplers are involved to minimize the deliberate selection error: the first tagged tree is circled clockwise by sampler one who collects one outside fruit from each quadrant of the tree from a belt extending from waist height to shoulder height, then he similarly samples the second tree counter-clockwise, the third tree clockwise, and the fourth tree counter-clockwise again; sampler two collects his samples similarly from trees five through eight, using the same sample container and resulting in 32 fruits/sample. Fruits of approximately the same size are selected.

Depending upon previously established possible analytical background con­tributions from the containers, the fruits are collected by clipping ( without handling) directly into four-gallon wide-mouth jars, suitable plastic bags, or strong paper bags. The code number of that sample, in waterproof ink on a durable card, is placed in the container and also written on the container which is then sealed and stored at 4° C. as promptly as possible. "Sweating" of fruits in jars or plastic bags may require subsequent "extraction" of the container for reliable analysis.

There are no established guides for sampling already harvested citrus fruits as in packing houses, from packed cartons, or in market displays for insecticide residues in quality assurance, surveillance, and monitoring programs. By broad analogy, the guides carefully estab­lished for this type of sampling for in-transit-added residues of bi-

78 F.A.GuNTHER

phenyl may be helpful, however; they are as follows (DE VOS 1968):

A random rather than a systematic sampling procedure is recommended, based upon statistical evaluations. To obtain a "sufficiently exact approximation" of the actual average biphenyl residue in a single shipping carton (about 40 pounds) of citrus fruits, 10 fruits randomly sampled by the random digit scheme produce an average biphenyl value with a standard deviation of about 10 percent of the actual mean biphenyl content of the carton to be sampled. When lots of cartons are involved, at least six cartons are sampled, with 10 fruits from each carton as a composite sample.

To illustrate the fruit-to-fruit variations involved, DE Vos (1968) analyzed a vertical half (63 fruits) of a carton of biphenyl-treated lemons and found 47 p.p.m. on the whole-fruit basis. The remaining 63 fruits were analyzed individually to yield a range of 23 to 98 p.p.m. with an average value of 52 p.p.m. The five individual layers in the half carton contained averages of 41, 57, 58, 56, and 48 p.p.m. of biphenyl.

VAN MmDELEM (1968) reports that 20 to 50 citrus fruits/sample (9 to 21 lb.) from 10-box harvested lots (900 lb.) are used in his program to evaluate pesticide residues. Until there is published a satisfactory demonstration that smaller numbers are adequate for ac­ceptably reliable average pesticide residue loads representative of a carton, a lot of cartons, or a bin of citrus fruits it seems reasonable to recommend at least 20 oranges or grapefruit/sample and 30 lemons/ sample for general pesticide residue evaluations of citrus fruits in the packing house bins, in cartons or boxes, or in market displays. On the other hand, FAHEY (1953) felt that large tree fruit required 50 fruits/ sample if differences of 20 percent of the mean are to be judged as significant at five percent odds, and LYKKEN (1963) felt that a 25-pound gross sample is the minimum for any crop. Our earlier work [CARMAN and GUNTHER, Unpublished (1950 and 1955)] with several insecticides and grove sampling demonstrated that 64 citrus fruits were required to meet FAHEY's (1963) criterion.

GARBER (1963) has presented an unusually thorough discussion of the proper statistical (biometrical ) design of general sampling pro­cedures and sample theory, including replication, randomization, and experimental design for residue evaluations.

c) Storage of fresh samples

The harvested citrus fruit is still a living, metabolizing plant part. Therefore the metabolism or other in situ alteration of penetrated in­secticides will not stop just because the fruit is picked. Samples must be refrigerated (---- 40 C.) just as soon as possible after collection, and they should be processed as soon as possible. Points on degradation curves, particularly, fit better when the curves are plotted if days in

Insecticide residues in citrus fruits 79

storage are included in the days elapsed since field treatment, which indicates that deposit penetration and residue alteration processes are not stopped by refrigeration. Freezing of citrus fruit samples is not recommended because the resulting ice crystals in the pulp rupture cells and thus could conceivably alter the residue distribution between albedo and pulp and also the enzymatically-induced residue metabolic picture. If samples must be deep frozen for more than 30 days, an aliquot of at least one sample should be analyzed before storage for comparison with the residue picture in the same sample after storage. When freezing is unavoidable, samples should be stored as intact fruits in tightly sealed plastic containers, and not as ground rind or pureed pulp because the enzyme activities of ground fruits are mark­edly different from those of intact fruits.

d) Processing of samples

The conversion of citrus fruits to dried citrus pulp cattle feed was discussed in section Vb). This present section is concerned with con­verting whole citrus fruits into solutions of the extractives from rind and pulp, the "processing" operation [see GUNTHER and BLINN (1955) for detailed discussions of this operation, VAN MIDDELEM (1963) for a resume, THORNBURG (1963) for a brief discussion of extraction pro­cedures, and SAMUEL and HODGES (1967) for an unusually thorough coverage of the literature on this subject].

As discussed earlier, in insecticide residue evaluation programs it can be very useful to be able to compare effective deposits and resi­dues from both washed and unwashed fruits throughout the courses of both degradation and persistence curves, not only to enhance the credibility of the total residue penetration and persistence picture, but also to guide predictions about probable residues in citrus products, the effects of rainfall on field treatments for pest control, and to assure further safety to the consumer in tolerance considerations.4o To pre­vent an excessive analytical burden, in most of these evaluations the collection of additional replicates of the field samples for both washed and unwashed "aliquots" can realistically be done for every other sampling interval to give at least two washed versus unwashed points on the degradation curve and three on the persistence curve.

Similarly, detailed experiences with about 30 essentially nonsys­temic insecticides and acaricides have demonstrated that it is not necessary to analyze every sample for pulp residues: every other sampling interval suffices, as was illustrated in Table X. If the analyses

40 It will be recalled that in the United States all citrus fruits are washed before being marketed or processed into products, except for mandarins and tangerines.

80 F.A.GUNTHER

promptly follow the field sampling, any deviation from the expected residues in the pulp (juice values of Table X) can be classified as an aberrant sample or as an actual pulp-penetration situation by calling for more frequent samples for pulp assay. If the analytical effort is on earlier processed extractives from a completed field program, however, there is no recourse but to repeat enough of the field program to estab­lish the true behavior of the residue; fortunately, Eureka lemons mature almost every month, Valencia oranges mature in the late spring and summer, and navel oranges mature in the late fall and winter in southern California so that the above decision does not mean a year's delay.41

With low dosage applications (i.e., less than 0.25 Ib./lOO gallons

t Rind

(weigh)

~ Mince 500g. to at least 4 mesh

!

Whole citrus fruits (32 fully-sized}

(2 or 3 replicates)

l Wash, if desired, then air dry

(see text)

t Weigh and peel cleanly

I

Albedo-free pulp (weigh)

t Double "core" each fruit

(weigh cares)

t Mince 500 g. to puree

Equilibrate 1 hr. with solvent (2 ml.lg.)

l Equilibrate 2 days with

solvent (l ml.lg.) at 4°C. ! Filter through

SharkSk(" paper

Two bottles at "extract"

Analyze one battle

(ca. 400 mi.)

I Store oQe bottle at 4°C. (ca. 400ml.)

t Filter or decant through

Sharkskin paper, separate phases

t Two bottles at "extract"

Analyze one bottle (~200ml.)

I Store one bottle at 4°C.(~ 200ml.)

Fig. 34. Flow diagram of processing operations for fresh citrus fruits

41 It will be recalled that the U.S. Food and Drug Administration usually regards residue data from these two varieties of oranges as interchangeable.

Insecticide residues in citrus fruits 81

and 1,500 gallons/acre) or unusually low gallonages/acre (i.e., 250 to 5(0), it may be necessary to use laboratory subsamples of 1,000 g. in­stead of the 500 g. recommended below; this decision depends upon the minimum reproducible detectability of the analytical method in the presence of the proper proportion of extraneous substrate extrac­tives.

The flow-diagram shown in Figure 34 illustrates the general pro­cedure for converting whole citrus fruits into extractive solutions for subsequent cleanup and analysis.

The detailed procedure is reproduced beltlw:

1. Preparation for peeling. - a ) Washed. - Wearing natural rubber gloves, gently brush each fruit with a soft-bristle brush in warm (45° to 50° C.) one-to-two percent detergent, mild soap, or alkaline soap ( footnote a, Table XVII) solution. Rinse each washed fruit thoroughly with running tap then distilled water, then stack the rinsed fruits comprising a sample on clean paper towels in wire baskets to air dry. Count and weigh the combined fruits.

fJ) Unwashed. - No treatment [except with samples for a degrada-

o ._(]) --.---~

A B c a b a b

Fig. 35. Special "buttonhook" peelers for citrus fruits, constructed of stainless steel or aluminum, and special serrated cork borer for cutting cylinders of pulp [GUNTHER and coworkers, Unpublished (1950)]. Peelers A and B are shown in right-angle views and also in cross-section; some workers prefer the round shape, others the flattened-oval shape

82 F.A.GUNTHER

tion curve the storage container should be rinsed thoroughly with the stripping ("extraction") solvent and the rinsings should be used as part of the equilibration solvent after the rind is minced (see Fig. 34)]. Count and weigh the combined fruits.

2. Peeling and coring. - Again wearing rubber gloves, each fruit is carefully peeled Havedo- and albedo-free with one of the special "buttonhook" peelers shown in Figure 35 and in the manner shown in Figure 36. Weigh both combined rind and combined peeled fruits. At

Fig. 315. The four sequential operations involved in quickly producing essentially albedo-free citrus fruits with a "buttonhook" peeler (see Fig. 35)

least one kg. of rind should be obtained from 32 fully-sized fruits. With samples for a degradation curve, lightly rinse the rubber gloves and the peeling tool with the stripping ("extraction") solvent, with the rinsings to be used as part of the equilibration solvent after the rind is minced (see Fig. 34).

Rinse each peeled fruit in running tap then distilled water and air dry as before in paper towel-lined wire baskets. Core each fruit twice from opposite sides of the equator to opposite poles with the No. 15 serrated cork borer shown in Figure 35. Using an ice pick to handle the resulting cylinders of pulp resting on clean paper towelling, with a clean scalpel cut about two mm. off each end of each cylinder to remove any adhering albedo; discard these ends. Weigh the combined cylinders or "cores": 32 fully-sized fruits should yield about 500 g. of cores.

Insecticide residues in citrus fruits 83

3. Mincing and equilibration 42. - The total sample of rind is "minced" or subdivided into pieces four-mesh or smaller in size on a Hobart food cutter 43 or Bau-Knecht all-purpose food cutter;44 the rind must not be ground in a meat grinder because of the heat gener­ated within a grinder. An aliquot of 500 ± 5 g. of the minced rind is then weighed into a stripping (equilibration) container such as a stainless steel stripping can (GUNTHER and BLINN 1955) or a two-quart wide-mouth Mason jar with threaded closure. Exactly two ml./g. of "extraction" solvent or solvent mixture 45 is then added, and the con­tainer is sealed with a thick aluminum foil gasket across the entire closure or lid and tumbled end-over-end at 50 to 70 revolutions/minute (r.p.m.) for one hour, as in the drum-tumbler of GUNTHER and BLINN ( 1955). The unopened container should be stored at 40 C. if the next step cannot be performed immediately after this equilibration.

The total sample of pulp cores (usually about 500 g.) is placed in the stainless steel stripping container 46 of GUNTHER and BLINN (1955) with one ml. of "extracting" solvent/g. of pulp and blended on the drill-press apparatus they described for one minute at about 4,000 r.p.m. The container is then sealed with a thick aluminum foil gasket and stored at 40 C. for about two days to complete the equilibration.

4. Segregation of "extracts." - About three-fourths of each rind equilibration mixture is decanted through a fluted 29-cm. Sharkskin 47

filter paper in about equal amounts into two screw-cap storage bottles of about 500-mI. capacity each. These bottles are capped with two

42 As stressed by GUNTHER and BLINN (1955) and GUNTHER (1962), the mixing and steeping of ground plant part with solvent is an equilibration, not an extraction (an "extraction" implies quantitative transfer of solute to solvent, as in a Soxhlet operation). For lack of a better term, these authors used the term "stripping" for these equilibration operations, but some confusion has since re­sulted because some authors use "stripping" to refer to a surface-only stripping operation, as dipping whole fruits into a container of solvent. There seems no alternative but to use the word "extract" in quotes in the present situation.

43 Model 84141 with gear attachment for accessory grinder, shredder, or vegetable slicer for general application; model 8141 without gear attachment. The Hobart Manufacturing Co., Troy, Ohio.

44 Bauknecht Grosskiichenmaschine AlIzweck Type KU 2-1. Kadin Co., Los Angeles, California; Bauknecht G.M.B.H., S. Heidenklinge 22, Stuttgart, Germany.

45 Depending upon the pesticide and its metabolic and other in situ altera­tion products, mixed solvents may be required. For example, it may be desirable to dehydrate the rind with isopropyl alcohol before adding a nonpolar solvent, or to use a methyl alcohol-chloroform mixed solvent for organophosphorus insecti­cides and their major metabolites. This type of "extraction" is discussed immedi­ately after the present subsection on processing directions.

46 Alternatively, an explosion-proofed Waring Blendor or Star-Mix may be used, but at low speed. High speeds above 4,000 r.p.m. yield intractable emulsions and suspensions with citrus pulp and most solvents.

47 High filtration rate and also high wet strength.

84 F. A. GUNTHER

layers of thin aluminum foil, the caps are screwed down tightly, the "extract" level is marked 48 with nonerasable ink, and the labelled bottles are stored at 40 C. awaiting cleanup and analysis.

Each cold pulp-equilibration mixture is decanted carefully to separate most (but not all) of the organic solvent phase from the aqueous phase. 1£ the former is less dense than the latter it can be decanted directly through Sharkskin filter paper 47 in about equal amounts into two screw-cap storage bottles; if the former is denser than the latter, the major part of the aqueous phase is discarded, the remainder of the mixture is poured gently into a one-liter separatory funnel, and the lower organic phase is drained through solvent-prewet Sharkskin filter paper 47 in about equal amounts into two screw-cap storage bottles. These bottles are capped with two layers of thin aluminum foil, the caps are screwed down tightly, the "extract" level is marked 48 with nonerasable ink, and the labelled bottles are stored at 40 C. awaiting cleanup and analysis.

5. Fortification of "extracts." - Fortifications of control aliquots for recovery evaluations and for possible storage-deterioration (see next subsection) are made at this time. As discussed by GUNTHER (1962), fortification prior to the "extract" stage is wasted effort for it provides neither field recovery data nor laboratory cleanup and analysis effi­ciency data: sorption and ligand formation in the presence of particles of substrate in the puree-organic solvent mixture may yield falsely low laboratory efficiency data and certainly do not resemble in the slightest the natures and magnitudes of these phenomena that undoubtedly 49

occur with molecularly penetrated insecticides in aged field samples, whereas fortification at this stage (normally at about 0.2 p.p.m. and at about four p.p.m.) does at least provide confirmation of the efficiency of cleanup and analysis in the presence of the proper proportions of substrate extractives. For storage deterioration studies the "extract" should be washed free of dehydrating solvent (if used) before forti­fication; otherwise, the solvent mixture plus extractives should be forti­fied before washing to evaluate washing losses (see next section), also.

6. Discussion of processing details. - If a dehydrating solvent is used - such as acetone (not recommended) or methyl, ethyl, or iso­propyl alcohol- it is usually necessary to wash it out of the nonpolar solvent with copious quantities of distilled water before the extractives

48 So as to detect possible evaporation losses after long storage. 49 There is an increasing awareness of and literature on this nonextractability

of major portions of many pesticides in many substrates (e.g., GUNTHER and BLINN 1955, KLEIN 1958 and 1960, KLEIN et al. 1959, HARDIN 1962, WHEELER and FREAR 1966, MUMMA et al. 1966, BENYON and ELGAR 1966, BURKE 1967, SAMUEL and HODGES 1967).

Insecticide residues in citrus fruits 85

solution is put into storage: insecticide chemicals in general seem to be more stable in nonpolar than in polar solvents.5o On the other hand, this water-polar-solvent mixture will contain most of the polar metabo­lites and other alteration products present and should be examined analytically if these products are of interest. Many insecticide chem­icals have such low solubilities in water (Table XI and GUNTHER et al. 1968) that this washing operation will have little effect on the final rind p.p.m. value, but this possibility must be investigated by the fortifications for laboratory efficiency discussed in the preceding sub­section. If dehydrating solvents are necessary, add the dehydrating solvent (0.5 to 1.0 ml./g.) to the rind, mix, allow to stand covered 10 to 30 minutes, then add the stripping solvent; the addition of a mixed solvent 51 in this room temperature equilibration does not always pro­vide efficient dehydration of citrus rind of the particle size recom­mended.

Though fresh citrus rind has a Dean-Stark moisture content of about 80 percent, the use of a dehydrating (polar) solvent is usually not necessary for evaluations of residues of the parent compounds which are mostly very soluble in the citrus oils, as discussed earlier, and which in tum are miscible with most nonpolar organic solvents such as the mixed hexanes. In some instances, however, it is desirable to use a solvent of intermediate polarity, such as chloroform, for ade­quate partitioning of sought molecule from rind into solvent; this choice is a matter of anticipation of proper solvent based upon the chemistry and expected biochemistry of the insecticide, any personnel hazard to be associated with the use of large volumes of the solvent, and subsequent interferences by the solvent and its impurities in the cleanup and determinative procedures. "Extraction" solvents to be avoided if at all possible are listed in Table XXIII, based upon the hazards or other disadvantages indicated when large numbers of samples are to be processed; also included are other "extraction" sol­vents, as based upon personal experiences, superior for the present purpose. In general, the mixed hexanes (mostly n-hexane) are the most widely used solvents for this purpose, especially for the organo­chlorine insecticides; organophosphates, carbamates, and some other insecticides are usually "extracted" with methylene chloride. The sol­vents used for the 32 insecticides in Tables VII and XXV, the subject of this report, are listed in Table XXIV along with the insecticide

110 However, see the next section [section X e)] for some exceptions. 111 Such as ten percent methyl alcohol in chloroform, or isopropyl alcohol in

mixed hexanes; this alcohol-chloroform mixture was first suggested. by MUMMA

et a1. (1966) to increase the extractability of certain pesticides sorbed onto sur­face-active plant constituents.

B6 F.A.GUNTHER

Table XXIII. "Extraction" or stripping solvents to be considered for preparing citrus extractiv86 in insecticide residue analyses

Solvent

Acetic acid

Acetone

Acetonitrile

Alcohols, alone

Benzene

Carbon disulfide

Comments a

Good solvent for most insecticides but sol­vent powers drop off rapidly with dilution, extracts too much extraneous material, diffi­cult to evaporate. Water soluble. Irritating vapors. Boils lIBoC., solidifies 16.7°C. Very expensive if adequately purified, exces­sive amounts required to counteract loss of solvent powers for nonpolar compounds with dilution, difficult to evaporate completely in presence of water, adsorbs very strongly to glassware. Water soluble. Highly flammable. Boils 56.5°C. Most recommended single solvent for most insecticides and their alteration products, very difficult to purify adequately for polarographic determination (however, see FORCIER and OLVER 1965), difficult to evap­orate. Miscible with many solvents including water [forms constant boiling mixture with water (16 percent), b.p. 76°C.]; immiscible most saturated hydrocarbons. Dissolves some inorganic salts. Poisonous-avoid breathing vapors, may cause skin irritation. Boils Bl.6°C. Methyl, ethyl, and isopropyl alcohols (see Isopropyl alcohol). Extract too many sugars, gums, lecithins, small polypeptides, etc. Flammable. Difficult to evaporate in pres­ence of water (constant boiling mixtures). Water soluble. Readily available in high purity. "Denatured" ethyl alcohol usually contains methyl alcohol, camphor, aromatic compounds (benzene, toluene) , pyridine bases, or others. Methyl alcohol boils 64.7·C., ethyl alcohol boils 7B.5·C., iso­propyl alcohol boils B2's"C. Very superior solvent for most insecticides, some polar and nonpolar alteration products. Water insoluble (0.1 percent) and easily quantitatively codistilled ("evaporated") in presence of excess water. Miscible many other solvents. Steam volatile. Highly flam­mable. Can produce bone marrow depression and aplasia if inhalec! over long periods. Avoid general use. Boils BO.1 ·C., solidifies 5.5°C. Superior, easily purified solvent for most insecticides and their alteration products. Water insoluble (0.3 percent, 20·C.) but

Insecticide residues in citrus fruits 87

Table XXIII. (Continued)

Solvent

Carbon tetrachloride

Chloroform

Cyclohexane

Dimethylformamide

Dimethyl sulfoxide

Dioxane

Ethyl acetate

Comments a

forms constant boiling mixture with water (2.8 percent), b.p. 42.6°C. Readily evap­orated, but offensive odor unless very pure; extremely flammable (e.g., hot steam pipes). Must be stabilized for long storage. Toxic. Boils 46.5°C., vapors sink to ground (need down- or back-draft hood). Excellent solvent for most insecticides, non­polar, noninflammable. Slowly decomposes on storage but readily purified by distilla­tion. Water insoluble (one mI./2,OOO m!. water) , readily evaporated. Toxic. Boils 76.7°C., vapors sink to ground (need down­or back-draft hood). Excellent solvent for most insecticides and their alteration products. Light sensitive; commercial product stabilized with about one percent isopropyl or other alcohol. Diffi­cult to maintain pure and aged solvent can contain strong oxidizing agent (phosgene). Dissolves traces of water (-0.5 percent, 25°C.), difficult to dry. Readily evaporated. Boils 61° to 62°C., vapors sink to ground (need down- or back-draft hood). Superior solvent for nonpolar compounds. Water insoluble. Readily evaporated. Diffi­cult to free from aromatic impurities. Flam­mable. Boils BO.7°C. Superior solvent for most insecticides and their alteration products. Water soluble, dif­ficult to evaporate in presence of water. Toxic. Boils 153°C. Very superior solvent for most insecticides and their alteration products. Decomposes violently in contact with acyl halides and perhaps other compounds-use with caution in new applications. Water soluble (hygro­scopic), difficult to evaporate in presence of water. Toxic. Flammable. Boils 1B9°C. Superior solvent for most insecticides and their alteration products. Forms peroxides on storage. Water soluble [forms constant boil­ing mixture with water (18 percent), b.p. 87.8°C.]. Difficult to evaporate, especially in presence of traces of water. Toxic. Flamma­ble. Boils 101.1 DC. Very superior solvent for organophosphorus insecticides and their alteration products (STORHERR and WATTS 1968) and some other classes of pesticides. One mI. dissolves

88

Table XXIll. (Continued)

Solvent

Ethyl ether

Hexanes, mixed

Isopropyl alcohol

Isopropyl ether

Methylene chloride

Methyl ethyl ketone

Nitromethane

F. A. GUNTHER

Comments a

in 10 mI. water (25°C.), difficult to evap­orate in presence of water (forms constant boiling mixture, b.p. 70.3°C.). Not recom­mended because too toxic for general use. Boils 77°C. Superior solvent for most insecticides and their alteration products. Difficult to keep free of peroxides. Dissolves about 1.5 per­cent water (25°C.), difficult to dry [forms constant boiling mixture with water (1.3 percent), b.p. 34.2°C.]. Easily evaporated. Highly flammable. Boils 34.6"C., vapors sink to ground (need down- or back-draft hood). Largely n-hexane. Inexpensive and readily purified. Most-used solvent for nonpolar or only slightly polar insecticides, particularly the organochlorine compounds. Water insol­uble, readily evaporated. Miscible with al­cohol, chloroform, ether. Flammable. Nar­cotic in high concentrations. Boils 60· to 70°C. See Alcohols, alone. Excellent dehydrating agent for plant and animal tissues with later transfer of solute to water immiscible sol­vent. Miscible with water [forms constant boiling mixture with water (12 percent), b.p. 80.4·C.], alcohol, ether, chloroform. Flammable. Not potable. Boils 82.5°C. See also Ethyl ether. Dissolves less water (-0.2 percent, 20°C.), but less easily evap­orated. Boils 68° to 69°C. Superior solvent for most insecticides and their alteration products. Difficult to purify and keep pure. Noninflammable. Toxic. Wa­ter insoluble (two ml./100 ml. water), read­ily evaporated. Another almost universal res­idue solvent. Boils 39.8·C., vapors sink to ground (need down- or back-draft hood). See Acetone, over which it has no real ad­vantages except reduced volatility. Solubility in water 27.5 percent, solubility of water in methyl ethyl ketone 12.5 percent (25°C.). Forms constant boiling mixture with water (11 percent), b.p. 73.4°C. Boils 79.6°C. Superior solvent for most insecticides and their alteration products. Slightly soluble wa­ter (9.1 percent), aqueous solutions acidic. Forms explosive mixtures in presence of al­kali. Flammable. Toxic. Not easily evapo­rated. Boils 101.2°C.

Insecticide residues in citrus fruits 89

Table xxm. (Continued)

Solvent Comments a

Propylene carbonate Recently recommended ( SCHNORBUS and PHILLIPS 1967) stable and versatile extract­ing solvent for many pesticides; the produc­tion of high purity propylene carbonate has been discussed by JASINSKI and KIRKLAND

( 1967). Noninflammable and nontoxic. Not readily evaporated. Soluble in most organic solvents, dissolves 8.3 percent water (non­hygroscopic). Boils 24l.7·C.

Pyridine Superior solvent for most insecticides and their alteration products. Water soluble [forms constant boiling mixture with water (three mols), b.p. 92· to 93·C.], difficult to evaporate especially in presence of water. Weak base. Offensive odor. Flammable. Steam volatile. Boils ll5· to ll6·C.

Toluene See Benzene. Less toxic than benzene. Boils llO.6·C.

2,2,4-Trimethylpentane (isooctane) Superior solvent for nonpolar insecticides and their nonpolar alteration products. Prac­tically insoluble water, soluble aromatic sol­vents, chloroform, ether, etc. Not readily evaporated. Flammable. May cause skin irri­tation. Boils 99.3·C.

Water Solvent for many pesticides (see GUNTHER et aZ. 1968). These solubilities can often be altered by addition of salts, alcohols, other solvents.

a Boiling points are at 760 mm.

manufacturer's recommendation for a suitable extraction solvent for use with nonoily crops.

In the procedure as recommended it is not necessary to collect all possible filtrate, finite volumes, or measured volumes of the extractive solutions from the filtration step. Equilibrations of the rind or the pulp with solvent are on a weight-volume basis, that is, 2.0 ml./1.0 g. or 1.0 ml./1.0 g., respectively. The "extract" therefore represents 0.5 g. of rind/mI. or 1.0 g. of pulp/mI., and the filtrates represent the same ratios unless there have been excessive evaporative losses during filtra­tion. Any subsequent operations during cleanup and analysis utilize pipetted aliquots of these solutions and the above ratios of g. of substrate/mI.

Tab

le X

XIV

. "E

xtra

ctio

n" s

olve

nts

that

wer

e us

ed f

or p

rese

nt i

nsec

tici

de r

esid

ue e

valu

atio

ns i

n ci

trus

fru

its

~

"Ext

ract

ion"

sol

vent

In

sect

icid

e C

omm

ents

in a

ppli

cati

on

chem

ical

U

sed

a R

ecom

men

ded

b to

cit

rus

frui

ts •

Ara

mit

e B

enze

ne, h

exan

e d

Ben

zene

A

lter

atio

n pr

oduc

ts n

ot s

tudi

ed

Azi

npho

s m

ethy

l H

exan

ed

Ace

tone

+ ch

loro

form

H

exan

e pr

obab

ly in

adeq

uate

B

idri

n B

enze

ne

Chl

orof

orm

E

ithe

r so

lven

t sat

isfa

ctor

y C

arba

ryl

Met

hyle

ne c

hlor

ide

Chl

orof

orm

E

ithe

r so

lven

t sat

isfa

ctor

y C

arbo

phen

othi

on

Hex

ane

d B

enze

ne

Ben

zene

pro

babl

y b

ette

r C

hlor

dane

H

exan

e d

Pen

tane

S

olve

nts

equi

vale

nt

~

Chl

orob

enzi

late

H

exan

ed

Ben

zene

A

lter

atio

n pr

oduc

ts s

olub

le in

hex

ane

DD

T

Ben

zene

, hex

ane

d B

enze

ne

Em

ulsi

on p

robl

ems

wit

h p

ulp

(b

enze

ne)

~

Dem

eton

A

ceto

ne o

r ch

loro

form

A

ceto

ne +

chlo

rofo

rm

0 D

iazi

non

Hex

ane

d H

exan

e

I D

icof

ol

Hex

ane

d H

exan

e D

ield

rin

Hex

ane

d H

exan

e D

imet

hoat

e M

ethy

lene

chl

orid

e M

ethy

lene

chl

orid

e D

ioxa

thio

n H

exan

ed

Hex

ane

EP

N

Ben

zene

B

enze

ne

Em

ulsi

on p

robl

ems

wit

h p

ulp

E

thio

n

Hex

ane

d H

exan

e H

epta

chlo

r H

exan

ed

Pen

tane

S

olve

nts

equi

vale

nt

Mal

athi

on

Car

bon

tetr

achl

orid

e C

arbo

n te

trac

hlor

ide

Mev

inph

os

Chl

orof

orm

C

hlor

ofor

m

Mor

esta

n H

exan

e d

Ace

tone

+ he

xane

H

exan

e al

one

pref

erre

d N

aled

A

cid

+ he

xane

A

cid

+ he

xane

A

cid

nece

ssar

y to

sta

bili

ze n

aled

N

eotr

an

Hex

ane

d B

enze

ne, h

exan

e N

icot

ine

Dil

ute

alka

li

Dil

ute

alka

li e

Om

ite

Ben

zene

, hex

ane

d B

enze

ne

Em

ulsi

on p

robl

ems

wit

h p

ulp

(b

enze

ne)

O

vex

Ben

zene

, hex

ane

d B

enze

ne

Em

ulsi

on p

robl

ems

wit

h p

ulp

(b

enze

ne)

Tab

le X

XIV

. (C

onti

nued

)

"Ext

ract

ion"

sol

vent

In

sect

icid

e C

omm

ents

in a

ppli

cati

on

chem

ical

U

sed

a I

Rec

omm

ende

d b

to c

itru

s fr

uit

s'

OW

-9 c

ompo

unds

H

exan

e"

Ben

zene

, hex

ane

Em

ulsi

on p

robl

ems

wit

h pu

lp (

benz

ene)

P

arat

hion

B

enze

ne

Ben

zene

A

cid

nece

ssar

y,!

emul

sion

pro

blem

s w

ith

pulp

P

hosp

ham

idon

M

ethy

lene

chl

orid

e M

ethy

l alc

ohol

In

suff

icie

nt d

ata

to f

avor

met

hyle

ne c

hlor

ide

Sch

rada

n C

hlor

ofor

m

Chl

orof

orm

---

TD

E

Hex

ane"

B

enze

ne, h

exan

e E

mul

sion

pro

blem

s w

ith

pulp

(be

nzen

e)

TE

PP

25

% A

queo

us a

ceto

ne

Chl

orof

orm

or

met

hyl a

lcoh

ol

Chl

orof

orm

ina

dequ

ate

Tet

radi

fon

Chl

orof

orm

11

Chl

orof

orm

---

a In

the

aut

hor'

s la

bora

tori

es.

bAs

re13

0rte

d b

y t

he

auth

ors

of t

he r

espe

ctiv

e re

sidu

e m

etho

ds i

n ZW

EIG

'S (

1963

-196

7) s

erie

s of

fiv

e vo

lum

es o

n pe

stic

ide

anal

yti-

cal

met

hods

or

in m

anuf

actu

rers

' bro

chur

es.

o A

lso

see

com

men

ts i

n pu

blis

hed

met

hod

(see

Tab

le V

II f

or r

efer

ence

s) f

or a

ddit

iona

l de

tail

s in

man

y in

stan

ces.

"

Mix

ed h

exan

es, l

arge

ly n

-hex

ane.

e

GU

NT

HE

R a

nd

BLI

NN

(1

95

5).

1

To

was

h o

ut

free

am

ines

an

d an

ilin

es

if w

ell-

know

n A

vere

ll-N

orri

s co

lori

met

ric

met

hod

is t

o b

e us

ed.

11 A

lso

acet

onit

rile

in

par

alle

l "e

xtra

ctio

ns."

The

chl

orof

orm

an

d a

ceto

nitr

ile

"ext

ract

s" w

ere

iden

tica

l in

tet

radi

fon

cont

ents

.

( g. ~

~ f s· ~ ...... ~ co ...

92 F. A. GUNTHER

e) Storage of extractives

Extractives solutions should be kept at 40 C. until cleaned up and analyzed, for the storage of these solutions at room temperature may result in hydrolyses or other alterations of the desired products to a degree sufficient to invalidate the final residue data. Even storage at 40 C. does not always prevent this storage deterioration, as illustrated in Table XXV. Azinphos methyl, diazinon, dicofol, dimethoate, More-

Table XXV. Illustrative storage stabilities at 4° to 10° C. of insecticides in citrus­fruit extractives solutions fortified at about one and at about ten p.p.m. (GUNTHER

and coworkers, Unpublished data accumulated over 20-year period)

Extractives Citrus Storage

Insecticide solvent variety period

(months)

Aramite n-Hexane Lemons 9 n-Hexane Oranges 9

Azinphos methyl n-Hexane Lemons 9 Bidrin Methylene chloride Oranges 20 Carbaryl Methylene chloride Lemons 8 Diazinon n-Hexane Oranges 19 Dicofol n-Hexane Oranges 17 Dimethoate Methylene chloride Oranges 4 Dioxathion n-Hexane Oranges 3 Morestan n-Hexane Lemons 6

n-Hexane Oranges 6 Omite Methylene chloride Oranges 8 OW-9 compounds n-Hexane Lemons 9

n-Hexane Oranges t 9 Parathion Benzene II Oranges 12

a To analytical method for unchanged parent compound. I> n.d. = none detectable.

Apparent loss of insecticide a

(%)

n.d.!> n.d.!> 20 0

n.d.!> n.d.!>, d

25-100 • 96 1-22 e n.d.!> 1-32 • 1-32 e 40 n.d.!> n.d.1> 30

C Possible evaporative losses if insecticide codistilled with sQlvent which evap­orated about 20 percent through aluminum-foil gasketed screw-cap closure on storage bottle.

d a-Naphthol was not detected either (GUNTHER et al. 1962 a). • Highly variable, fortified at one to ten p.p.m. t Both navel and Valencia oranges. II Plus traces of hydrochloric acid used to wash out free amines and anilines.

stan, Omite, and parathion showed marked storage losses of parent compounds to the analytical methods utilized. The mechanisms of these losses are not known. Fortification of control sample extractives before storage and analysis after storage, or a few analyses of field sample extractives followed by analyses of the same extractives solu­tions after storage, are essential to support the analytical integrity of

Insecticide residues in citrus fruits 93

stored extractives. It is generally conceded that storage for no longer than one month, particularly at temperatures below 0° C.,52 does not require this elaborate validation, but this concession may not be valid for some materials.

The practice of opening and utilizing for the subsequent analyses only one of the two bottles of extractives representing each sample is highly recommended, for this practice keeps in reserve an amount of extractives-plus-residue sufficient to accommodate laboratory mishaps, apparently aberrant residue data when the entire program is surveyed, evaluated, and interpreted, and any referee analyses that may be re­quired. It is our practice to maintain these reserve stored extractives for one year for these contingencies.

f) The analysis

In this category are included concentration operations, cleanup, and final determinations. These steps have been discussed in detail by many authors (e.g., GUNTHER and BLINN 1955, GUNTHER 1962, ZWEIG

1963 et seq., SAMUEL and HODGES 1967). Except for concentration operations, cleanup and final analysis are individual matters for each insecticide and the reader is referred to the references listed in Table VII for details for each chemical herein considered.

A general procedure for qualitatively and quantitatively examining qitrus fruit rind of unknown pesticide treatment history for its residue content has been developed by MESTRES (1968 [see section VIII a)] as based upon the general MILLS (1959) procedure for small soft fruits. MESTRES uses four m!. of isopropyl alcohol plus two m!. of hexane/g. of rind for a first-stage "extraction," followed by two more ml. of hexane/g. of the once-extracted rind. Water is then added to the combined extractives solution in the ratio of eight m!. of water/g. of starting rind; the resulting equilibrated aqueous phase is discarded and the hexane "extract" is dried and concentrated to about 10 m!. Part of this concentrate is then divided into three fractions, on five percent water-deactivated Florisil columns, for further gas chromatographic segregation (DC-200 or Q F -1) and measurement:

Eluate 1 (45° to 60° C. hexane only) will contain aldrin, benzene­hexachloride, chlordane, DDE, heptachlor and its expoxide, TDE, and toxaphene, plus some other pesticides.

Eluate 2 (ethyl ether: hexane, 20:80, first cut) will contain carbo­phenothion, chlorobenzilate, diazinon, dicofol, dieldrin, endrin, methoxychlor, parathion, and tetradifon.

112 Benzene solutions may solidify at about 5° C. and burst full containers.

94 F.A.GUNTHER

Table XXVI. Insecticides in citT1J8 rind extractives separable and measurable by the MESTRES (1968) procedure compared with those currently important to

California citriculture

Segregable Importance to California citrus industry

Insecticide and measurable

Hazleton by MESTRES Laboratories, Inc. University uf California

(1968) (1967) a recommendations II

Aldrin Yes No importance Not recommended Aramite No Useful " Registration withdrawn Azinphos methyl Yes Useful Recommended Benzenehexachloride Yes No importance Not recommended Bidrin No Key material Useful II Bromophos ethyl Yes -- Not recommended Carbaryl No Key material Recommended Carbophenothion Yes Nonessential Recommended Chlordane Yes Key material Recommended 6

Chlorobenzilate Yes Key material Recommended DDT (and DDE) Yes Key material Recommended Demeton Yes Nonessential Recommended Diazinon Yes Nonessential Not recommended Dichlorvos Yes -- Not recommended Dicofol Yes Key material Recommended Dieldrin Yes Nonessential Not recommended Dimethoate Yes Useful " Recommended " Dioxathion No Key material Recommended DN compounds No No importance Not recommended Endosulfan Yes -- Not recommended Endrin Yes -- Not recommended EPN No No importance Not recommended Ethion No Nonessential Recommended Fenitrothion Yes -- Not recommended Heptachlor Yes Useful " Not recommended HETP No Nonessential Not recommended Lindane Yes No importance Not recommended Malathion Yes Key material Recommended Methoxychlor Yes -- Not recommended Methyl parathion Yes Key material See Parathion Mevinphos Yes Useful Recommended Morestan No -- Recommended " Naled Yes Useful Recommended Neotran No Useful " Registration withdrawn Nicotine No Nonessential Not recommended Omite No -- Useful II Ovex r Yes Nonessential Recommended Parathion Yes Key material Recommended Phenthoate Yes -- Not recommended Phosphamidon Yes Useful Recommended Schradan No -- Not recommended TDE Yes Key material Recommended

Insecticide residues in citrus fruits 95

Table XXVI. (Continued)

Insecticide

TEPP Tetradifon Toxaphene

Segregable and measurable

by MESTRES

(1968)

No Yes Yes

Importance to California citrus industry

Hazleton Laboratories, Inc. University of California

(1967) a recommendations b

Nonessential Nonessential Key material

Recommended Recommended Recommended

a See Table I; quoted by Hazleton Laboratories, Inc. (1967) and HAZLETON (1968) from unpublished table prepared by G. E. CARMAN and H. C. LEWIS.

b See Table XXVII. "Recommended" means that the chemical is useful against certain insects or mites and may be used safely under specified conditions of dosage, formulation, and timing.

C Nonbearing trees. Ii Registration pending. e Granular formulation only. f Chlorfenizon in France.

Eluate 3 (ethyl ether:hexane, 20:80, second cut) will contain more diazinon, malathion, and methyl parathion, plus some other pesticides.

Some other compounds not segregated by this procedure are deter­mined by direct gas chromatography on DC-200 of the initial extrac­tives concentrate, as azinphos methyl, demeton, dichlorvos, dimethoate, mevinphos, naled, and phosphamidon, according to MESTRES (1968).

The MESTRES (1968) procedure separates and measures the insecti­cides and acaricides relisted in Table XXVI. In this table his list has been expanded to include additional materials currently important to California citriculture as outlined by Hazleton Laboratories Inc. ( 1967) (see Table I) and as recommended by inclusion in the 1968/ 1969 "Treatment Guide for California Citrus Crops" of the Division of Agricultural Sciences of the University of California (see "References" section). These three listings are not identical, for MESTRES' concern is largely with pesticides currently used on both fruits and vegetables on the European market, whereas the other two listings relate strictly to insect and Illite control on California citrus trees. In Table XXVI, a "No" in the MESTRES column denotes either that he did not consider the chemical or that he cannot deterInine it by his method; a blank in the Hazleton Laboratories Inc. column denotes that the material is currently not yet considered (materials not yet registered for this use in the United States), that it is not useful for the present purpose, or that it is an abandoned material; and a "Not recommended" in the University of California column denotes that a material was not recom-

96 F. A. GVNTHER

mended, by exclusion from the list, because of a decline in or absence of usefulness, withdrawal of registration, or lack of registration for use on citrus trees.

In any citrus fruit residue analytical program, concentrations and evaporations of citrus extractives solutions should be performed care­fully because of the possibilities of codistillation of some insecticides (GUNTHER and BLINN 1955, HINDIN 1967) with the large quantities of limonene 53 always present. The Kuderna-Danish technique (GUNTHER and BLINN 1955) is the only recommended technique for this purpose, with the lower one-third of the evaporation flask bathed in steam and always with the Snyder column prewet with solvent. After subsequent steps (e.g., partitioning) to separate the bulk of the oils, other tech­niques can be used; for example, a very convenient and efficient way to transfer many insecticides from an organic solvent into water is to place the solution and about 10 mI. of water in a rotating vacuum evaporator at about SOo C. and under slight vacuum until the organic solvent has evaporated.

XI. Miscellaneous aspects and conclusions

This entire program is a part of the extensive and continuing effort to maintain the quantity and the quality of modem agricultural pro­duction. As insecticides are displaced by more efficient or less trouble­some newer materials, or are supplanted by new ones to counter the re­sistance phenomenon, it becomes of interest to compare compounds and dosages used during the developmental stages for registration with those currently recommended. It is also of interest to compare the developmental residue data with amounts actually being found in current commercial practice often many years later (see section VIII), and to conjecture about the adequacy of surveillance and monitoring programs in relation to the developmental programs that form the nucleus of this review. These two considerations comprise the first two parts of this section.

The third part of this section is a discussion of the paucity of data on insecticide metabolites and other alteration products in citrus fruits and products, with conjecture about probable metabolites in situ in fresh fruits from the indirect evidence of some of the sloping persist­ence curves earlier presented.

The fourth and fifth parts of this section are truly miscellaneous in that they are concerned with citrus insecticides in the grove environ­ment and with the deposition and persistence of insecticides on citrus leaves versus citrus fruits.

113 A major component of citrus oi1s.

Tab

le X

XV

ll.

Sum

mar

y co

mpa

riso

n o

f do

sage

s us

ed i

n de

velo

ping

pre

regi

stra

tion

res

idue

dat

a ve

r8tU

I do

sage

s cu

"en

tly

reco

mm

ende

d b

y th

e D

ivis

ion

of

Agr

icul

tura

l Sc

ienc

es o

f th

e U

nive

rsit

y o

f C

alif

orni

a (1

96

8/1

96

9)

Dos

age

(act

ual c

ompo

und)

Inse

ctic

ide

Cit

rus

Cit

ed in

text

M

axim

um c

urre

ntly

rec

omm

ende

d va

riet

y

Fig

. lb

./lo

o g

al.

Gal

./ac

re

lb./

loo

gal

. G

al./

acre

Ara

mit

e L

emon

s 3

0.3

1,50

0 R

egis

trat

ion

wit

hdra

wn

-O

rang

es

-0.

3 1,

500

Reg

istr

atio

n w

ithd

raw

n -

Azi

npho

s m

ethy

l A

ll 4

1.0

1,50

0 1.

0 2,

500

Bid

rin

Lem

ons

--

-R

egis

trat

ion

pend

ing

-O

rang

es

5 1.

4 2,

500

Reg

istr

atio

n pe

ndin

g -

Car

bary

l A

ll 6

1.0

1,50

0 1.

0 2,

500

Car

boph

enot

hlon

A

ll 7

0.6

1,50

0 0.

4 1,

500

Chl

orda

ne

All

8 2.

0 20

0 5

lb./

acre

, gr

anul

ar a

-

Chl

orob

enzi

late

L

emon

s 9

0.25

1,

000

0.25

1,

500

Ora

nges

-

--

0.25

1,

500

DD

T

All

10

2.

0 25

0 0.

7 2,

500

Dem

eton

A

ll

31

Var

ious

V

ario

us

1/8

1,

500

Dia

zino

n L

emon

s 11

0.

5 1,

500

Not

rec

omm

ende

d -

Ora

nges

11

0.

5 1,

500

Not

rec

omm

ende

d -

Dic

ofol

A

ll 12

0.

4 1,

500

0.4

1,50

0 D

ield

rin

Ora

nges

13

1.

0 1,

500

Not

rec

omm

ende

d -

Dim

etho

ate

All

14

1.0

2,50

0 0.

5 b

500

b

Dio

xath

lon

All

15

0.4

2,50

0 0.

4 1,

500

DN

com

poun

ds

All

--

-N

ot r

ecom

men

ded

-E

thio

n A

ll 16

1.

0 2,

500

0.4

1,50

0 H

epta

chlo

r L

emon

s 17

2.

0 35

0 N

ot r

ecom

men

ded

-

S'

'" a o· ~

~ f 5'

o ~ ..... ~ ~

Tab

le X

XV

II.

(Con

tinu

ed)

Dos

age

(act

ual

com

poun

d)

Inse

ctic

ide

Cit

rus

Cit

ed in

text

M

axim

um c

urre

ntly

rec

omm

ende

d va

riet

y

Fig

. Ib

./l0

0 g

al.

Gal

./ac

re

Ib./

l00

gal

. G

al./

acre

Mal

athi

on

All

18

0.8

2,50

0 0.

9 2,

500

Mev

inph

os

All

-

Var

ious

V

ario

us

2.0

500

Mor

esta

n A

ll 19

1.

0 2,

500

0.25

II

500

II

Nal

ed

All

-

_0

_

0

2.5

500

Neo

tran

L

emon

s 20

0.

5 1,

500

Reg

istr

atio

n w

ithd

raw

n -

Ora

nges

2

0

0.5

1,50

0 R

egis

trat

ion

wit

hdra

wn

-O

rnit

e O

rang

es

21

0.5

1,50

0 R

egis

trat

ion

pend

ing

-O

vex

All

22

0.

5 1,

000

0.5

2,50

0 O

W-9

com

poun

ds

Ora

nges

23

0.

6 1,

500

Wit

hdra

wn

-P

arat

hion

A

ll 24

1.

0 1,

500

0.6

1,50

0 P

hosp

harn

idon

O

rang

es

-_

0

_c

1.0

250

Sch

rada

n L

emon

s 32

0.

1% s

olut

ion

Not

rec

omm

ende

d -

Ora

nges

32

0.

1% s

olut

ion

Not

rec

omm

ende

d -

TD

E

All

25

1.0

250

2.0

500

TE

PP

A

ll

-V

ario

us

Var

ious

-0

.8

250

Tet

radi

fon

All

26

0.

25

1,50

0 0.

25

1,50

0 T

oxap

hene

O

rang

es

-_

c

_c

1.2

500

a S

oil a

ppli

cati

on o

nly.

/)

Onl

y on

non

bear

ing

tree

s or

mat

ure

tree

s w

ith

no fr

uit p

rese

nt.

C R

esid

ue d

ata

deve

lope

d b

y i

ndus

try,

per

sist

ence

cur

ves

not

avai

labl

e.

co

00

;.<.l

~ f

Insecticide residues in citrus fruits 99

a) Current insecticide dosages in California

In Table XXVII are listed the insecticides and acaricides previously mentioned in connection with California citriculture along with the dosages cited in text and used for registration and tolerance classifica­tion as well as the dosages currently recommended by the Division of Agricultural Sciences of the University of California (1968/1969). It will be noted that with few exceptions dosages have been generally reduced over those initially utilized; also, initial field programs often used double the expected commercial dosages so as to accommodate emergency pest-control treatments without exceeding a tolerance value. In addition, several of the insecticides and acaricides formerly recom­mended have now been withdrawn from commercial usage or they are no longer recommended because they have been displaced or replaced by newer materials (see Table XXVI, footnote b).

b) Adequate developmental, surveillance, and monitoring programs for pesticide residues

Residue data developed in California to aid in the licensing, regis­tration, and tolerance classmcation of new insecticides and acaricides for use in citriculture represent the maximum residues that could be present on and in unwashed fruits at harvest time, in compliance with the needs of good agricultural practice. Residues actually found in a commendable limited but continuing and presumably expanding qual­ity assurance market survey program of the approximately 300,000-acre California-Arizona Citrus League interests in general are con­siderably lower than the developmental residues (see especially section VIII). The reasons for these lowered residue levels probably include the facts that in commercial practices a single lot of fruit from a particular grove loses its homogeneity in large-scale packing house operations, and in continuing pest-control practices rarely are the maximum dos­ages of developmental programs utilized over large acreages. To illustrate, residues on a whole-fruit basis approximately 30 days after treatment from the developmental program with the JI azleton Labora­tories, Inc. (1967) ''key materials" (Table I) underlying Figures 1, 6, 8 to 18, and 22 to 26 are compared in Table XXVIII with those in the California-Arizona Citrus League program [section VIII b) J; it is assumed that the latter residues are for fruits harvested, sampled, and analyzed at least 30 days after treatment. Dicofol, dioxathion, mala­thion, parathion, and TDE occur in amounts probably greater than expected, but all of these residues are below the corresponding toler­ance values of 10, 2.8, 8.0, 1.0, and 7.0 p.p.m., respectively (Table I); alsQ; Jrom Table XXVII it will be noted that since the developmental

100 F.A.GUNTHER

Table XXVllI. Comparison of key insecticide residues in citrus fruits from the developmental program versus those currently in market samples

Insecticide

Aramite Carbaryl Chlordane Chlorobenzilate DDT Diazinon Dicofol Dieldrin Dioxathion Ethion Heptachlor Malathion Ovex Parathion TDE Tetradifon

Maximum residues (p.p.m., whole-fruit basis) found

Developmental program a

-0.1 1.3-3.1 a

2.2 2.9 1.0

0.1-0.5 a 1.5

1.8-2.7 a 0.3-1.3 a 1.7-3.2 a

0.6 0.1 0.5 0.1 a 0.2

0.8-1.1 6

CACL b program

None ° 0.2

None C

1.9 1.0 0.3 3.0 0.1 2.6 0.1 0.02 0.5 0.02 0.7 1.1 0.3

• From Figures 1, 6, 8 to 18, 22 to 26 at the 30-day interval. b Califomia-Arizona Citrus League program. Data from Table XXI. ° None detectable by the method utilized. a Two varieties. 6 Range from three analytical methods.

programs the recommended dosages of carbaryl, chlordane, chloro­benzilate, DDT, ethion, ovex, and parathion have been decreased, whereas that for dioxathion has been increased and diazinon, dieldrin, and heptachlor are no longer recommended.

Developmental programs cannot be strictly colligative but also must account for major metabolites and other alteration products, as discussed earlier and also in the next subsection. With this information, toxicologists and pharmacolOgists decide whether routine surveillance (suspected high residues, directed samples) and monitoring (quality assurance, no directed samples) programs for residue determinations are to include or suitably compensate for certain metabolites in the walytical method to be used for each crop (e.g., aldrin + dieldrin, DDT + DDE, demeton sulfones, paraoxon, etc.). Several methods re­spond to derivatives of the parent insecticide, and sometimes these method-derived derivatives are also the established or probably in situ alteration products; a suitable method should therefore distinguish the two (or more) species involved and also measure them as separated

Insecticide residues in citrus fruits 101

entities. Often the chemistry of the method indirectly can provide this information, as in the measurement of the a-naphthol before and after the laboratory hydrolysis of carbaryl extractives mixtures obtained with a stripping solvent that "extracted" both compounds from the substrate, or the measurement of sulfoxides and sulfones before and after the oxidation of C-S-C containing isolates.

Sampling citrus fruits for these various programs was discussed in section X b).

c) Insecticide metabolites and other alteration products in citrus fruits

With but a few exceptions with citrus fruits, little is known about the natures or the magnitudes of metabolic or other in situ alteration products from these insecticides and acaricides, and nothing is known of these products in canned, concentrated, and frozen citrus juices, citrus pulp cattle feed, citrus oils, or citrus marmalades and other rind products. Aldrin and heptachlor are no longer recommended for Cali­fornia citrus pest control so their well-established and toxic metabolic epoxidation products are of little concern, although (Table XXVIII) some heptachlor is apparently still used in some areas; the direct use of the epoxide of aldrin (dieldrin) is clearly minimal (Table XXVIII). The residue occurrences of the highly toxic, metabolically produced oxons of some of the organophosphorus compounds, such as malaoxon and paraoxon, have not been evaluated at all. These oxons are gener­ally shorter-lived than the parent compounds through base-catalyzed hydrolytic mechanisms at ordinary temperatures. The present residue picture is certainly incomplete in this regard because citrus juices buffered on the acid side may "protect" some of them against their assumed, rapid hydrolysis [see section Va)].

The systemic insecticides demeton, mevinphos, and schradan have been evaluated in terms of metabolic products in citrus juices with clear evidence of reasonably rapid conversion to biologically inactive products (see section VII).

Similarly, as earlier discussed in text, multiple analytical methods applied to the rind residues of a few of these insecticides and acari­cides have demonstrated (see section IX) major conversion of carbo­phenothion residues (Fig. 7), possible conversion of chlorobenzilate residues (Fig. 9), slight conversion of dicofol residues (Fig. 12), and major conversion of tetradifon residues (Fig. 26). Unless the time­disappearance of residues (as demonstrated by the negative slopes of all persistence curves for insecticides on and in citrus fruits) is due to volatilization of parent compound and/or alteration products or to the formation of analytically unresponding alteration products, all of these materials are converted in major part to other compounds. Reserva-

102 F. A. GUNTHER

tions must be attached to this deductive inference, however, for it is difficult to understand, for example, how the total organically bound chlorine method as used for major parts of the chlordane (Fig. 8), DDT (Fig. 10), dieldrin (Fig. 13), heptachlor (Fig. 17), Neotran (Fig. 20), and TDE (Fig. 25) residue evaluations could miss major stable alteration products with the "extraction" procedures utilized, especially when the total chloride value was interpreted as unchanged parent molecule (GUNTHER and BLINN 1955, GUNTHER 1962 and 1966). On the other hand, certain of the total residue analytical procedures utilized afforded reasonable assurances that expected major hydrolyti­cally-produced alteration products would be detected by the method but separately from the parent compound, as with azinphos methyl (Fig. 4), Bidrin (Fig. 5), carbaryl (Fig. 6), diazinon (Fig. 11), dioxathion (Fig. 15), malathion (Fig. 18), Morestan (Fig. 19), ovex (Fig. 22), and parathion (Fig. 24); accounting for these major hydrolytic prod­ucts does not completely Hatten the persistence curve in a single instance.

d) Citrus insecticides in the grove environment

Efficient control especially of insects and mites in citrus groves currently involves the applications of large gallonages of sprays/acre, with usually from 90 to 120 trees/acre. Full-coverage sprays can in­volve as much as 2,500 gallons/acre (e.g., see Figs. 5, 14, 15, 16, 18, and 19 and Table XXVII) although the usual range is 1,000 to 1,500 gallons/acre. Sometimes much less is used in concentrate spraying operations or in "skirt and trunk" spraying operations which may in­volve as little as 200 gallons/acre (e.g., see Figs. 8, 10, 17, and 25 and Table XXVII). Dosages have ranged from 0.25 lb. to 2.0 lb. of actual chemical/lOO gallons of finished spray, or from less than 2.5 lb. (see Table XVIII) to 35 lb. of pesticide chemical/acre (Figs. 3 through 26, 28 through 30, and 32 and Tables V, VI, VIII, IX, XIII, XIV, XIX, and XXVII). Usual dosages are from about five to about 25 lb.jacre, sometimes with multiple applications in a given year and usually with more than one insecticide/year.

WES1LAKE and GUNTHER (1966) report that it is not unusual to find 50 percent or more of the pesticide chemical unaccounted for in the materials balance in the treated area immediately after applica­tion; other workers have estimated that at least half the spray directed at a plant never hits the target surface and that a large part of the spray that aChtally hits the foliage subsequently drips to the ground, especially in full-coverage applications.

In addition to drift to adjacent areas, much of this "lost" pesticide will settle or run off to the ground, and aged foliage and some fruits containing residues will drop to the ground. In addition, excess de-

Insecticide residues in citrus fruits 103

posits (Figs. 1 and 28 through 30) may be lost to air dispersion or sloughing to the ground, and these excess deposits may amount to at least half the originally deposited material (GUNTHER and BLINN 1955).

Once on the ground, these pesticides (including fungicides applied to the trees as well as herbicides applied directly to the soil) are subject to photodecomposition and the usual soil-environment types of hydrolyses and degradations by the soil fauna and flora. They are also subject to leaching and other migration-inducing influences from ir­rigation practices, rainfall, and wind dislodgment of surface-exposed soil. From the dosages cited above it is clear that the citrus grove environment is annually exposed to a variety of pesticides in con­siderable amounts.

As with many other tree-fruit and other crops, it is clear that run­off and leach waters from citrus groves must be suspect of containing an impressive variety of pesticide chemicals (e.g., see Tables I and XVI). Actual analytical data to support this statement are not avail­able, to the author's knowledge, for California-Arizona citriculture. Similarly, drift, the other major environmental contamination aspect of citrus pest control, has not been extensively studied, but several in­vestigators have established drift long distances downwind from pesti­cide treatments applied to many types of crops, including some tree fruits. Drift is usually considered also to include rain out and snowout (WESTLAKE and GUNTHER 1966, p. 113). Because of the mechanics of pesticide applications to almost any-sized plant, a certain amount of drift is unavoidable even in the absence of obvious air currents; ap­plications to mature trees clearly increase the amounts of spray that will drift. Most investigators categorize drift according to sizes of air­borne particles, and it has not been unusual to find the smaller par­ticles many miles from the point of application.

An even more neglected area is the release of pesticides in vapor fonn to the grove environment. Considering that a mature citrus tree has perhaps 100,000 leaves of about 50 cm.2 total surface area each, and bearing an initial deposit of at least 10 p.g./cm.2 [JEPPSON and GUNTHER, Unpublished (1968)], a treated tree exposes to the sun and air at least 50 g. of pesticide chemical more or less uniformly distributed over at least 5,000,000 cm.2 (about 1,920 ft. 2 ) of total leaf surface. This situation is ideally suited to photodecomposition and air oxidation and volatilization, including steam distillation via the transpiring leaves.

This situation was studied in some detail for parathion wettable powders (CARMAN et al. 1952) with segregation of analytical data into both air-borne particulate matter and vapor (gaseous parathion) both with treated foliage in the field and with treated fruits in the labora­tory. Technical grade parathion has a vapor tension of 0.03 to 0.04 po

104 F. A. GUNTHER

at 680 to 750 F. (BRIGlIT et al. 1950, WILLIAMS 1951) and 0.7 po at 1300 F. (WILLIAMS 1951), as contrasted with 0.013 po for p,p'-DDT at 1220 F. (BALSON 1947).

1. Parathion vapors from field-treated oranges. - The apparatus used is shown schematically in Figure 37. Charcoal-filtered air at 4.0

r----------------i Illuminated incubator

I I I I I I I I I I I I

IAi I I r I I I ~-----------------~

Fly cage

Fig. 37. Schematic diagram of all-glass apparatus to collect parathion vapors from treated oranges (redrawn from CARMAN et al. 1952). All joints are held together with springs

Ib./in.2 was forced into the sample jar at the rate of 300 cc./hour; emergent air was passed through a glass fly cage or directly into two benzene-containing scrubbers in series. The benzene scrubbing solu­tions were analyzed colorimetrically at 24-hour intervals; housefly assays involved 25 insects/test for 24-hour periods. Tests were run at 600 to 800 F. both in total darkness and under "daylight" fluorescent illumination. Demonstrable traces of parathion were recovered, via the air stream, from both varieties of oranges treated with either a wet­table powder formulation or an emulsive concentrate formulation, with more parathion released from recently treated fruits (cf. Fig. 24). The concentrations in the air streams were not sufficient to kill the houseflies, however. Thus, only small amounts of parathion were re­leased to the air stream.

2. Parathion vapors in treated groves. - The apparatus used is shown schematically in Figure 38. In this instance the absorbing solu­tion was 95 percent ethyl alcohol, maintained at constant volume by the reservoir on the right, and periodically pumped by means of the

Insecticide residues in citrus fruits

Fine 8inter­plate funnel

Filter paper I

Check valves

VacUUID pump via now meter

Ball joint

Colll'8e sinter bubbler

105

Fig. 38. Schematic diagram of all-glass field apparatus to collect and measure parathion vapors in treated orange groves (redrawn from CARMAN et al. 1952). All joints are held together with springs

syringe pump through a 10-cm. quartz cell in a spectrophotometer set at 274 mp., the absorption maximum of parathion in this solvent. In use, this apparatus was placed in the centers of 900 to 1,800 treated mature­tree blocks. Airflow through the absorber was 150.0 l./hour; sampling periods were 30 minutes each, with from six to 10 consecutive sam­plings/test. Since particulate matter of the particle size of the 25 percent wettable powder formulation was excluded from contact with the scrubbing solvent by the design of the sampling apparatus, any parathion detected would have been in the vapor state. Tests at field temperatures ranging from 75 0 to 101 0 F. demonstrated less than 0.17 mg. of parathion vapors/m.B in the air from any of the treated groves, but subsequent filter tests [CARMAN and GUNTHER, Unpublished (1953)] demonstrated parathion-containing particulate matter in mov­ing air in similar groves treated with the same wettable powder formu­lation. These data supported the results of other workers sampling air both in formulating plants and in citrus groves in other areas (see CARMAN et al. 1952 for review). Thus, the treated surfaces of the trees released very small amounts of parathion vapor to the air, but readily demonstrable amounts of parathion-containing particles of the pre­sumed original wettable powder to air moving through the trees.

106 F. A. GUNTHER

e) Deposition and persistence of insecticides on leaves versus fruits

In connection with the OW-9 compounds fruit residue program underlying Figure 23 [GUNTHER and JEPPSON, Unpublished (1962)], ancillary measurements for residues on and in the leaves of the same treated Valencia orange trees were made, with quantitative persistence comparisons of residues from several dosages on and in the rind versus those on and in the foliage. Leaves selected (120/sample) were from the same portions of the same eight treated trees as the fruits repre­sented in Figure 23, were from the same cycle of growth, and aver­aged about 50 cm.2 total leaf surface each; they were collected by direct snipping into two-quart Mason jars, with 15 leaves/tree. Results were calculated in terms of residues on area (p.g.jcm.2), volume (p.g.j cm.a ), and weight (p.p.m.) bases for the whole fruits and on area and weight bases for the leaves.

Areas and volumes of the fruits were established by measuring the polar and two equatorial axes for each fruit and use of TURRELL'S ( 1946) tables; areas of leaves were determined with the photoelectric "Arealimeter" described by GUNTHER and BLINN (1955). Fruit rind was obtained and processed as described earlier; leaves were tumbled at 58 r.p.m. for one hour with one liter of solvent/120-leaf sample. The laboratory recoveries (laboratory efficiencies) from fortified sam­ples are reproduced in Table XXIX. As with the other residue-penetra-

Table XXIX. Laboratory recoveries of OW-9 compounds from fortified samples of Valencia orange rind, pulp, and leaves (JEPPSON et al. 1968)

Substrate

Rind Pulp Leaves

No. of samples

39 19 31

Recovery" (%)

92 ± 11 86 ± 17 75± 9

"Laboratory efficiency. Fortifications were in the 0.1 to 40.0 p.p.m. range for rind and pulp and 0.1 to 10.0 p.g./cm.2 for leaves.

tion evaluations of nonsystemic acaricides, there were no detectable residues of the OW-9 compounds in any of the approximately 200 treated and control samples of pulp involved.

The residue data for the fruit rind and for the leaves are collated in Tables XXX and XXXI.

HaH-lives of the OW-9 compounds on and in leaf tissues are con­sistently about haH those on and in the rind tissues, indicating less "protection" of the leaf residue. Washing removed very little of the initial deposits from either substrate, demonstrating very rapid pene-

Tab

le x

xx.

Hal

f-li

ves,

ini

tial

depo

sits

, an

d re

sidu

e va

lues

for

OW

-9 c

ompo

unds

at

five

dosa

ges

on a

nd i

n V

alen

cia

oran

ge r

ind

on a

rea,

vo

lum

e, a

nd w

eigh

t ba

ses

of

the

who

le f

ruit

(J

EP

PS

ON

et

al.

1968

)

Init

ial

depo

sit

c 60

-Day

res

idue

a

120-

Day

res

idue

Ii

Dos

age

a H

alf-

life

b

(oz.

/10

0 g

al.)

(d

ays)

IL

g./

cm.2

jL

g./c

m.3

p.

p.m

. jL

g./c

m.2

!l<

g./

cm.3

p.

p.m

. jL

g./c

m.2

;J

Lg.

/om

.3

p.p.

m.

3 U

nwas

hed

100,

100

, 10

5 4

4 3

2.5

3 2

1.5

2 5

Unw

ashe

d 90

, 9

0,1

10

5

5 7

3 3

3 2

2 W

ash

ed

70,

90,

95

4 5

4 3

3 2

2 2

7 U

nwas

hed

95,

130,

130

7

6 6

5 5

4 4

3 W

ash

ed

120

6 -

-4

--

3 -

9 U

nwas

hed

105,

120

-

8 7

-5

4 -

3 W

ash

ed

85,

90,

105

7 7

6 5

5 4

3 3

12

Unw

ashe

d 10

5, 1

05,

108

10

9 8

7 6

5 4

4

a O

unce

s ac

tual

"co

mpo

und"

as

the

85 p

erce

nt e

mul

sive

co

nce

ntr

ate/

l00

gal

lons

, 1,

500

gall

ons/

acre

. S

ee a

lso

Fig

ure

23.

b

Sep

arat

e va

lues

fro

m s

epar

ate

pers

iste

nce

curv

es.

c B

y ex

trap

olat

ion

of

degr

adat

ion

curv

es b

ack

to z

ero

day.

a

Fro

m p

ersi

sten

ce c

urve

s.

1 2 1 3 - 3 2 4

r g. g: ~ g: fR er ~ ~ [ 1il" .... S

108 F.A.CUNTHER

Table XXXI. Half-lives, initial deposits, and residue values for OW-9 compound.! at two dosages on and in Valencia orange leaves on both area and weight bases

(JEPPSON et al. 1968)

Dosage a Initial deposit 0 60-Day residue d 120-Day residue d

(oz./lOO Half-life b

gal. ) ( days) ILg./cm.2 p.g./cm.2 p.p.m. p.g./cm.2 p.p.m. p.p.m.

---5

Unwashed 60,50 5 350 0.8 70 0.4 30 Washed 55,65 3 300 0.7 60 0.4 25

7 Unwashed 55,66 7 450 1.5 130 0.7 50 Washed 60,50 6 400 1.2 110 0.5 50

a Ounces actual "compound" as the 85 percent emulsive concentrate/100 gal-lons, 1,500 gallons/acre. See also Figure 23.

b Separate values from separate persistence curves. • By extrapolation of degradation curves back to zero day. d From persistence curves.

tration of this particular mixture; the half-lives, of course, were not affected by washing.

For all practical purposes, OW-9 compounds rind deposits and residues were the same regardless of whether calculated on an area­of-whole-fruit basis, on a volume-of-whole-fruit basis, or on a weight­of-whole-fruit basis. On an area basis, the leaves accepted initial de­posits exactly equivalent to those accepted by the fruits for the same two dosages of Table XXXI, yet aged residues in the leaves were much less than those in the fruits, as demonstrated by the respective half-lives. On a weight (p.p.m.) basis, the leaves accepted and re­tained apparently immensely greater deposits than the fruits: the ratio for leaves of p.p.m. to p.g.jcm.2 was consistently 70 to one, whereas for fruits on a rind basis only 54 the ratio of p.p.m. to p.g.jcm.2 was consistently five to one.

Comparisons of deposits and residues from the same treatment on both fruits and foliage from the same citrus trees have not previously been reported. It is apparent from these data that residues in p.p.m. on and in citrus foliage cannot be directly compared with residues in p.p.m. on and in citrus fruits without a large interpolation factor; the generality of this statement in relation to other fruit crops and their foliage is not implied by the present limited study. However, the above findings may guide others who wish to evaluate deposits on and residues on and in citrus fruits and leaves in terms of the biologi-

54 According to Table III, mature Valencia oranges have 18.7 ± 6.3 percent rind. The data in Table XXX are on a whole-fruit basis.

Insecticide residues in citrus fruits 109

Table XXXII. Chemical identifications of insecticides and acaricides mentioned in text (Chemical Abstracts style)

Insecticide or acaricide

aldrin

allethrin

anthracene Aramite

azinphos methyl

benzenehexachloride benzopyrene BHC Bidrin

biphenyl bromophos ethyl

carbaryl carbophenothion

chlordane

chlorobenzilate DDD DDE DDT demeton

diazinon

dibenzanthracene dibenzopyrene dichlorvos dicofol dieldrin

dimethoate

dinocap dioxathion DN compounds

DNBP endosuHan

endrin

Chemical designation

1,4:5,8-Dimethanonaphthalene, 1,2,3,4,IO,IO-hexachloro-1,4,4a,5,8,8a-hexahydro-, endo-exo isomer Cyclopropanecarboxylic acid, 2,2-dimethyl-3-( 2-methyl­propenyl) -, 2-allyl-4-hydroxy-3-methyl-2-cyclopenten-1-one Anthracene SuHurous acid, 2- (p-tert-butylphenoxy )-1-methylethyl-2-chloroethyl ester Phosphorodithioic acid, O,O-dimethyl ester, S-ester with 3-( mercaptomethyl ) -1,2,3-benzotriazine-4 ( 3H) -one 1,2,3,4,5,6-Hexachlorocyclohexane Benzo[a or e]pyrene See benzenehexachloride Phosphoric acid, dimethylester, ester with cis-3-hydroxy-N, N-dimethylcrotonamide Diphenyl Phosphorothioic acid, O,O-dimethyl 0-( 4-bromo-2,5-dichlorophenyl) ester Carbamic acid, methyl-, I-naphthyl ester Phosphorodithioic acid, S-[p-chlorophenyl) -thiomethyl]-, O,O-diethyl ester 4:7-Methanoindan, 1,2,4,5,6,7,8,8a-octachloro-3a,4,7,7a­tetrahydro-, endo isomer Benzilic acid, 4,4'-dichloro-, ethyl ester See TDE Ethylene, 1,I-dichloro-2,2-bis( p-chlorophenyl)-Ethane, 1,1,1-trichloro-2,2-bis( p-chlorophenyl)­Phosphorothioic acid, 0,0-diethyl-0-[2-( ethylthio ) ethyl] ester mixed with 0,0-diethyl-S-[2-( ethylthio ) ethyl] ester Phosphorothioic acid, O,O-diethyl 0-( 2-isopropyl-6-methyl. 4-pyrimidinyl) ester Dibenz[a,c or a,f]anthracene Dibenzo[ a,i]pyrene Phosphoric acid, 2,2-dichlorovinyl-, dimethyl ester Benzhydrol, 4,4' -dichloro-a.- ( trichloromethyl)-1,4:5,8-Dimethanonaphthalene, 1,2,3,4,IO,IO-hexachloro-6, 7-epoxy-1,4,4a,5,6,7,8,8a-octahydro-, endo-exo isomer Phosphorodithioic acid, O,O-dimethyl ester, S-ester with 2-mercapto-N-methylacetamide Crotonic acid, 2-( I-methylheptyl)-4,6-dinitrophenyl ester p-Dioxane-2,3-diyl ethyl phosphorodithioate Phenol, 2-cyclohexyl-4,6-dinitro- (and related phenols), salts of Phenol, 2-sec-butyl-4,6-dinitro. 5-N orbomene-2,3-dimethanol-, 1,4,5,6,7,7 -hexachloro-, cyclic sulfite 1,4; 5,8-Dimethanonaphthalene, 1,2,3,4,10, IO-hexachloro-6, 7 -epoxy-1,4,4a,5,6,7,8,Ba-octahydro-, endo-endo isomer

110 F. A. GUNTHER

Table XXXII. (Continued)

Insecticide or acaricide

EPN ethion fenitrothion heptachlor

HETP lindane malaoxon

malathion

methoxychlor methylcholanthrene methyl parathion mevinphos

Morestan

naled

Neotran nicotine Omite

OMPA ovex OW-9 compounds paraoxon parathion Phenthoate

Phosdrin phosphamidon

pyrethrins

sabadilla schradan tartar emetic TDE TEPP tetradifon toxaphene

Chemical designation

Phosphorothioic acid, phenyl-, O-ethyl O-p-nitrophenyl ester Ethyl methylene phosphorodithioate Phosphorothioic acid, O,O-dimethyl 0-4-nitro-m-tolyl ester 4:7-Methanoindene, 1,4,5,6,7,8,8a-heptachloro-3a,4,7,7a­tetrahydro-, endo isomer Hexaethyltetraphosphate gamma-Isomer of 1,2,3,4,5,6-hexachlorocyclohexane Succinic acid, mercapto-diethyl ester, S-ester with 0,0-dimethyl phosphorothioate Succinic acid, mercapto-diethyl ester, S-ester with 0,0-dimethyl phosphorodithioate Ethane, 1,1,1-trichloro-2,2-bis( p-methoxyphenyl)-3-Methylcholanthrene Phosphorothioic acid, O,O-dimethyl 0- (p-nitrophenyl) ester Crotonic acid, 3-hydroxy-, methyl ester, dimethyl phos­phate Carbonic acid, dithio-, cyclic S,S-ester with 6-methyl-2,3-quinoxalinedithiol Phosphoric acid, 1,2-dibromo-2,2-dichloroethyl-, dimethyl ester Methane, bis( p-chlorophenoxy)-1-3-( 1-Methyl-2-pyrrolidyl)-pyridine Sulfurous acid, 2- (p-tert-butylphenoxy) cyclohexyl 2-propynyl ester See schradan Benzenesulfonic acid, p-chloro-, p-chlorophenyl ester See Aramite, but with (1-methylethyl)n where n = 2 or 3 Phosphoric acid, diethyl-, p-nitrophenyl ester Phosphorothioic acid, O,O-diethyl O-p-nitrophenyl ester Phosphorodithioic acid, O,O-dimethyl S-( ethylmercapto­phenylacetate) ester See mevinphos Phosphoric acid, dimethyl ester, ester with 2-chloro-N,N­diethyl-3-hydroxycrotonamide Cyclopropaneacrylic acid, 3-carboxy-a,2,2-trimethyl-1-methyl ester, 3-ester with 4-hydroxy-3-methyl-2- (2,4-pentadienyl) -2-cyclopenten-1-one (Pyrethrin II) and cyclopropanecarboxylic acid, 2,2-dimethyl-3- (2-methylpro­penyl) ester with 4-hydroxy-3-methyl-2-( 2,4-pentadienyl)-2-cyclopenten-1-one (Pyrethrin I) Sabadilla mixture Pyrophosphoramide, octamethyl-Antimony potassium tartrate Ethane, 1, 1-dichloro-2,2-bis ( p-chlorophenyl)­Ethyl pyrophosphates Sulfone, p-chlorophenyl-2,4,5-trichlorophenyl-Chlorinated camphene containing 67 to 69 percent chlorine

Insecticide residues in citrus fruits 111

cal effectiveness of field-applied pesticide chemicals. A wettable powder formulation might behave differently from this emulsive con­centrate formulation, but the possibility exists that similar behavior for other insecticides and other formulations may be encountered.

Acknowledgments

The data herein summarized are from the many published and some unpublished field and laboratory analytical results obtained over the past 20 to 25 years in cooperation especially with E. L. Atkins, Jr., G. E. Carman, W. Ebeling, W. H. Ewart, L. R. Jeppson, D. L. Lind­gren, J. C. Ortega, and H. T. Reynolds, and their many other asso­ciates, on the staff of this Department of Entomology, and with the technical residue-analytical laboratory assistance of many chemists largely under the supervision of R. C. Blinn, J. H. Barkley, and W. E. Westlake of these laboratories; several of the investigations reported were carried out with the technical and other assistance of residue chemists from various members of the agricultural chemicals industry working cooperatively in our laboratories. Valuable suggestions in early discussions and drafts of the manuscript were made by J. H. Barkley, G. E. Carman, A. G. Salter, W. E. Shilling, H. E. Swisher, L. R. Wells, and W. E. Westlake.

Summary

Southern California is a major area in the United States for de­veloping insecticide and acaricide residue information on and in citrus fruits, especially with Valencia and navel oranges and with Eureka lemons. During the past 25 years the residue behaviors of more than 35 organic insecticides and acaricides applied in the field to these citrus fruits have been evaluated in terms of locales of residues on and in the fruits and of their persistence curves and half-lives under field conditions, usually for about 120 days after application to mature trees bearing fully-sized fruits. Many of these compounds accumulate in major part in the flavedo in the oil-containing tissues, and nonsystemic materials generally do not penetrate in significant quantities into the edible portions of the fruits.

The significance of these conclusions is discussed in detail in terms of pesticide residue legislation around the world and resultant toler­ance considerations. Detailed residue behaviors for these non systemic chemicals on and in fresh fruits are evaluated in terms of dosages, formulations, citrus varieties, and adequacies and deficiencies of the total residue analytical methods utilized. The limited data available on transfer of these residues to major citrus products and the con-

112 F. A. GUNTHER

sequences of fruit washing on these residues are also presented. A few systemic insecticides are discussed with reference to occurrence in citrus juices.

That the developmental residue evaluation programs and resultant tolerances are indeed protecting the consumer is interpreted via mar­ket survey programs currently in progress.

Multiple residue methods for citrus fruits provide much more in­cisive data than single methods, as illustrated with several compounds. To aid residue analysts in working with this difficult substrate, full details of the total analytical methodology involved are presented, both for fresh fruits and for dried citrus pulp cattle feed; a laboratory­scale preparation of the latter is included.

Because recommended dosages of particular chemicals often may be lowered with time, comparisons are made of the original versus the present dosages in terms of tolerances and quality assurance programs. Despite this massive effort, there is a dearth of information on the metabolic and other fates of insecticide residues in citrus rind and in citrus fruit products including juices.

Complete degradation and persistence curves are reproduced and discussed for 23 insecticides and acaricides on and in citrus fruits. The deposition of insecticides in citrus grove environments, and the move­ment of insecticides in the air in citrus groves, is briefly discussed.

Resume*

Les residus d'insecticides dans les agrumes et les principaux produits d' agrumes de la C alifornie

Le sud de la Californie est une region essentielle des Etats-Unis pour l'obtention de renseignements sur les residus d'insecticides et d'acaricides a l'etude sur et dans les agrumes, en particulier les oranges Valencia et Navel, et les citrons Eureka. Au cours des 25 dernieres an­nees, on a evalue Ie comportement des residus de plus de 35 insecti­cides et acaricides organiques appliques en plein champ sur agrumes. Cette evaluation a ete exprimee en donnees sur l' emplacement des residus sur et dans les fruits, leurs courbes de persistance et leurs durees de demi-vie dans des conditions de plein champ, generalement jusqu'a 120 jours environ apres Ie traitement, les arbres ayant atteint la pleine production et portant des fruits completement developpes. La plupart de ces composes s'accumulent en majeure partie dans les tissus du flavedo contenant des huiles. Les produits non systemiques ne penetrent generalement pas dans les parties comestibles du fruit.

L'interpretation de ces conclusions est discutee de maniere detail­lee en fonction des legislations des differents pays du monde sur les

• Traduit par S. DORMAL-VAN DEN BRUEL.

Insecticide residues in citrus fruits 113

residus de pesticides et des considerations qui en decoulent pour les tolerances. Le comportement des residus des composes chimiques non systemiques sur et dans les fruits frais est examine en detail en fonc­tion des doses d'application, des formulations et des varietes d'agrumes, ainsi que la validite et les lacunes des methodes appliquees Ii l'analyse des residus totaux. On presente egalement des donnees limitees sur Ie passage de ces residus dans les principaux produits d'agrumes ainsi que sur l' effet du lavage sur les residus. On examine quelques insecti­cides systemiques, quant Ii leur presence dans les jus d'agrumes.

Les programmes d' execution courante de controle des marches permettent de verifier si les programmes d'evaluation des residus Ii l' etude et Ies tolerances qui en decoulent protegent effectivement Ie consommateur. Comme Ie montrent plusieurs composes, les methodes de detection multiple des residus fournissent beaucoup plus de don­nees pertinentes pour les agrumes que ne Ie font les methodes de detection simple. En vue d'aider l'analyste dans son travail sur ce substrat difficile, on presente en detail la methodologie analytique complete qui se re£ere Ii la fois aux fruits frais et aux pulpes d'agrumes sechees destinees Ii l'alimentation du betail.

Etant donne que les doses d'utilisation recommandees pour certains produits chimiques peuvent souvent decroitre au cours du temps, des comparaisons des doses initiales par rapport aux doses actuelles sont faites en se re£erant aux tolerances et aux programmes de garantie de qualite. Malgre ces efforts considerables, il y a un defaut d'informa­tions sur Ie metabolisme et les autres processus d' evolution des residus d'insecticides dans les ecorces d'agrumes.

Zusammenfassung*

Insektenbekiimpfungsmittelriickstiinde in californischen Zitrusfriichten und -Produkten

In den Vereinigten Staaten ist Siid-Califomien ein Hauptgebiet fiir die Entwicklung von Informationen iiber Insekten- und Milbenbe­kiimpfungsmittelriickstande, besonders in Valencia- und Navel-Orangen und in Zitronen. Wahrend der letzten 25 Jahre wurde das Riick­standsverhalten von mehr als 35 organischen Insekten- und Milbenbe­kampfungsmitteln, die im Feld auf diesen Zitrusfriichten angewendet wurden, im Sinne der Riickstandsanwesenheit auf und in den Friichten und ihrer Bestandigkeitskurven und Halbwertszeit unter Feldbedin­gungen gewohnlich fUr 120 Tage nach Anwendung auf erwachsenen Baumen, die normalgrosse Friichte tragen, ausgewertet. Viele dieser Verbindungen sammeln sich hauptsachlich in der "Flavedo," den ollialtigen Geweben, an, und nicht-systemische Stoffe dringen im allge-

• Obersetzt von MARGARETE DUSCH.

114 F.A.GUNTHER

meinen nur in unbedeutenden Mengen in die essbaren TeUe der Friichte ein.

Die Bedeutung dieser Schlussfolgerungen wird im Einzelnen im Sinne von Schadlingsbekampfungsmittelriickstandsgesetzgebung auf der ganzen Welt und der sich daraus ergebenden Toleranzerwagun­gen diskutiert. Detaillierte Riickstandsverhalten fiir diese nicht-syste­mischen chemischen Praparate auf und in frischen Friichten werden im Sinne von Dosierungen, Formulierungen und Zitrus-Varietaten, Zu­langlichkeiten und Unzulanglichkeiten der gesamten benutzten riick­standsanalytischen Methoden ausgewertet. Die begrenzt verfiigbaren Daten in Dbertragung dieser Riickstande auf hauptsachliche Zitrus­produkte und die Folgen des Friichtewaschens auf diese Riickstande werden auch dargestellt. Einige systemische Insektenbekampfungsmit­tel werden hinsichtlich ihres Vorkommens in Zitrus-Saften diskutiert.

Ob die entwickelten Riickstandsauswertungsprogramme und die sich daraus ergebenden Toleranzen wirklich den Verbraucher beschiit­zen, wird durch Marktgutachtenprogramme, die laufend im Gange sind, erklart. Mehrfache Riickstandsmethoden liefem viel einschnei­dendere Daten als einzelne Methoden, wie an verschiedenen Verbin­dungen veranschaulicht wurde. Urn Riickstandsanalytikem beim Arbeiten mit diesem schwierigen Substrat zu helfen, werden volle Einzelheiten der gesamten in Mitleidenschaft gezogenen analytischen Methodologie, sowohl fiir frische Friichte als auch fiir Viehfutter aus getrocknetem ZitrusfruchtHeisch, dargestellt.

Da empfohlene Dosierungen von besonderen Chemikalien oft mit der Zeit abnehmen, werden Vergleiche der urspriinglichen mit den verhandenen Dosierungen im Sinne von Toleranzen und Qualitats­sicherstellungsprogrammen angestellt. Trotz dieser grossen Anstren­gung herrscht ein Mangel an Informationen iiber Stoffwechsel- und andere Schicksale der InsektenbekampfungsmitteIriickstande in der Zitrusschale.

References

ANDERSON, C. A., D. MACDoUGALL, J. W. KESTERSON, R. HENDRICKSON, and R. F. BROOKS: Effects of processing on Guthion residues in oranges and orange products. J. Agr. Food Chern. 11,422 (1963).

Anonymous: Reduced tolerance for DDT. Federal Register, Feb. 19 (1968 a). - Italian pesticide regulation for fruits and vegetables. Gazzetta Ufficiale della

Repubblica Italiana, No. 28, pp. 634-639, Feb. 1 (1968 b). ATKINS, E. L., R. C. BLINN, T. R. FUKUTO, and F. A. GUNTHER: Residues on

oranges resulting from the use of DDT, parathion, Phosdrin, and TDE for the control of orangeworms. J. Econ. Entomol. 54, 455 (1961).

BALSON, E. W.: Vapor-pressure measurement. III. An effusion manometer sensitive to 5 x 10-6 millimeters of mercury: Vapor pressures of DDT and other slightly volatile substances. Trans. Faraday Soc. 43, 48 (1947).

Insecticide residues in citrus fruits 115

BARNES, M. M., G. E. CARMAN, W. H. EWART, and F. A. GUNTHER: Fruit surface residues of DDT and parathion at harvest. Adv. Chern. Series 1, 112 (1950).

BENYON, K. I., and K. E. ELGAR: The analysis for residues of chlorinated insecti­cides and acaricides. Analyst 91, 143 (1966).

BLINN, R. C., G. E. CARMAN, W. H. EWART, and F. A. GUNTHER: Residual be­havior of various insecticides on and in lemons and oranges. J. Econ. Entomol. 52, 42 (1959 a).

--, R. W. DORNER, J. H. BARKLEY, L. R. JEPPSON, F. A. GUNTHER, and C. C. CASSIL: Locale of aged Tedion residues on citrus fruits. J. Econ. Entomol. 52,723 (1959 b).

-- --, F. A. GUNTHER, and M. J. KOLBEZEN: Microdetermination of the acaricide ethyl p,p'-dichlorobenzilate (Chlorobenzilate). J. Agr. Food Chern. 2, 1080 (1954).

BOYCE, A. M.: Personal communication (1946). BRIGHT, N. F. H., J. C. CUTHILL, and N. H. WOODBURY: Vapor pressure of

parathion and related compounds. J. Sci. Food Agr. 1, 344 (1950). BURKE, J. A.: Report on chlorinated insecticides and miticides. J. Assoc. Official

Anal. Chemists 50, 575 (1967). CARMAN, G. E., W. H. EWART, M. M. BARNES, and F. A. GUNTHER: Absorption

of DDT and parathion by fruits. Adv. Chern. Series 1, 128 (1950). --, F. A. GUNTHER, R. C. BLINN, and R. D. GARMUS: The physical fate of

parathion applied to citrus. J. Econ. Entomol. 45, 767 (1952). COol', J. W.: Persistence of residues in foods. In C. O. Chichester (ed.): Research

in pesticides, pp. 205-212. New York: Academic Press (1965). CRAFTS, A. S., and C. L. Foy: The chemical and physical nature of plant surfaces

in relation to the use of pesticides and to their residues. Residue Reviews 1, 112 (1962).

DE Vos, R. H.: Sampling and analysis for biphenyl residues in citrus fruit. Proc. Internat. Citrus Symposium, Riverside, Calif., Mar. 16-26 (1968). In press.

Division of Agricultural Sciences of the University of California: 1968/1969 Treat­ment guide for California citrus crops. California Agricultural Experiment Station Extension Service, Berkeley, Calif. (1968/1969).

EBELING, W.: Analysis of the basic processes involved in the deposition, degrada­tion, persistence, and effectiveness of pesticides. Residue Reviews 3, 35 ( 1963).

EWART, W. H., H. S. ELMER, and F. A. GUNTHER: Parathion treatments for the control of citricola scale on citrus in California. J. Econ. Entomol. 44, 598 (1951).

FAHEY, J. E.: Digest of the literature, 1925 through 1952, relating to sampling of crops for spray residue analyses. U. S. Department of Agriculture Mimeo., 59 pp. (1953).

FORcmR, G. A., and J. W. OLVER: Simplified purification of acetonitrile for elec­troanalytical applications. Anal. Chern. 37, 1447 (1965).

FREAR, D. E. H.: Pesticide residue investigations on raw agricultural commodities. Pennsylvania State University Agr. Expt. Station Bull. 703 (1963).

GARBER, M. J.: Statistical evaluation of results and sampling procedures. In G. Zweig (ed.): Analytical methods for pesticides, plant growth regulators, and food additives, Vol. 1, pp. 491-530. New York: Academic Press (1963).

GASTON, L. K., J. H. BARKELY, D. E. OTT, F. E. HEARTH, L. R. JEPPSON, and F. A. GUNTHER: Persistence of Morestan residues on and in citrus fruits by five complementary analytical methods. J. Agr. Food Chern., in press (1969).

GUNTHER, F. A.: Aspects of the chemistry of DDT. J. Chern. Ed. 22, 238 and 279 (1945).

116 F.A.CUNTHER

-- Chemical studies of DDT as an insecticide. 30th Ann. Meeting, Pacific Slope Branch Amer. Assoc. Econ. Entomol., Riverside, Calif., June 26-28 (1946).

- Unpublished data (1950). -- Instrumentation in pesticide residue determinations. Adv. Pest Control Re-

search 5, 191 (1962). -- Advances in analytical detection of pesticides. In: Scientific aspects of pest

control, pp. 276-302. Nat. Acad. Sci.-Nat. Research Council, Washington, D.C., Publ. No. 1402 (1966).

-- Current status of pesticide residue methodology. In: Biological effects of pesticides in mammalian systems. N.Y. Acad. Sci., New York City, in press (1968 a).

- Unpublished data (1968 b). --, and R. C. BLINN: Analysis of insecticides and acaricides. New York: Inter-

science (1955). -- -- Persistng insecticide residues in plant materials. Ann. Review Entomol.

1,167 (1956). -- -- Ultraviolet spectrophotometric microdetermination of the acaricide 4,4'­

dichloro-alpha-(trichloromethyl)-benzhydrol (FW-293). J. Agr. Food Chem. 5,517 (1957 a).

--, and F. BUZZETI'I: Occurrence, isolation, and identification of polynuclear hydrocarbons as residues. Residue Reviews 9, 90 (1965).

--, and L. R. JEPPSON: Ovotran residues in citrus. University of California Citrus Expt. Sta. Mimeo., 20 pp" Nov. 15 (1951).

-- -- Residues of p-chlorophenyl-p-chlorobenzenesulfonate (Compound K-6451) on and in lemons and oranges. J. Econ. Entomol. 47, 1027 (1954).

--, and W. E. WESTLAKE: Studies of organic insecticide residues in California citrus fruits and products. Proc. Intemat. Citrus Symposium, Riverside, Calif., Mar. 16-26 (1968). In press.

--, and M. M. BARNES, and G. E. CARMAN: Removal of DDT and parathion residues from apples, pears, lemons, and oranges. Adv. Chem. Ser. 1, 137 (1950).

--, J. H. BARKLEY, and W. H. EWART: Harvest residues of apparent dieldrin in peel and juice of navel oranges. J. Econ. Entomol. 47, 1033 (1954).

--, R. C. BLINN, and]. H. BARKLEY: Infrared procedure for quantitative deter­mination of residues of 2,4,4',5-tetrachlorodiphenyl sulfone (Tedion) on and in citrus fruit peel. J. Agr. Food Chem. 7, 104 (1959 a).

-- --, and G. E. CARMAN: Residues of Sevin on and in lemons and oranges J. Agr. Food Chem. 10, 222 (1962 a).

-- -- -- Residues of ethion on and in lemons and oranges as determined by an infrared spectrophotometric procedure. J. Agr. Food Chem. 10, 224 (1962 b).

-- --, L. R. JEPPSON, J. H. BARKLEY, C. J. FRISONE, and R. D. GARMUS: Field persistence of the acaricide 4,4'-dichloro-alpha-( trichloromethyl)-benz­hydrol (FW-293) on and in mature lemons and oranges. J. Agr. Food Chem. 5,595 (1957 b).

-- --, M. J. KOLBEZEN, J. H. BARKLEY, W. D. HARRIS, and H. S. SIMON: Microestimation of 2- (p-tert-butylphenoxy) isopropyl-2-chloroethyl sulfite res­idues. Anal. Chem. 23, 1835 (1951).

--, F. BUZZETI'I, and W. E. WESTLAKE: Residue behavior of polynuclear hydro­carbons on and in oranges. Residue Reviews 17, 81 (1967).

--, G. E. CARMAN, R. C. BLINN, and J. H. BARKLEY: Persistence of residues of Guthion on and in mature lemons and oranges and in laboratory-processed citrus "pulp" cattle feed. J. Agr. Food Chem. 11, 424 (1963).

Insecticide residues in citrus fruits 117

-- --, L. R. JEPPSON, J. H. BARKLEY, R. C. BLINN, and G. G. PATCHETT: Residual behavior of S-( p-chlorophenylthio ) methyl O,O-diethyl phosphoro­dithioate (Trithion) on and in mature lemons and oranges. J. Agr. Food Chern. 7, 28 (1959 b).

--, W. H. EWART, J. H. BARKLEY, and R. T. MURPHY: Persistence of residues of dimethoate on and in mature Valencia oranges and in laboratory-processed citrus pulp cattle feed. J. Agr. Food Chern. 13, 548 (1965).

-- --, R. C. BLINN, H. S. ELMER, and G. B. WACKER: Field persistence com­parisons of residues of the insecticide, Diazinon, in lemons and Valencia oranges and eHects on juice flavor. J. Agr. Food Chern. 6, 521 (1958 a).

--, J. W. HYLIN, and R. E. SPENGER: Nature of chlorine interferences in total halogen methods of analysis of organochlorine pesticide residues in plants. J. Agr. Food Chern. 14,515 (1966).

--, L. R. JEPPSON, J. H. BARKLEY, L. M. ELLIOTT, R. C. BLINN, and C. L. DUNN: Persistence of residues of 2,3-p-dioxanedithiol S,S-bis( O,O-diethyl phosphorodithioate) as an acaricide on and in mature lemons and oranges. J. Agr. Food Chern. 6, 210 (1958 b).

-- --, and G. B. WACKER: Persistence of chlorobenzilate residues in mature lemon fruits. J. Econ. Entomol. 48, 372 (1955).

--, D. L. LINDGREN, M. I. ELLIOT, and J. P. LA DUE: Persistence of certain DDT deposits under field conditions. J. Econ. Entomol. 39, 624 (1946).

--, W. E. WESTLAKE, and P. S. JAGLAN: Reported solubilities of 738 pesticide chemicals in water. Residue Reviews 20, 1 (1968).

HAlIDEN, L. J., and C. T. SARTEN: Comparison of five extraction procedures for the recovery of DDT residues in field-treated collards. J. Assoc. Official Agr. Chemists 45, 988 (1962).

HARRIS, T. H., and J. G. CUMMINGS: Enforcement of the Federal Insecticide, Fungicide, and Rodenticide Act in the United States. Residue Reviews 6, 104 (1964).

Hazleton Laboratories, Inc.: Final report: Market research project for 1966-1967. Dec. 8 (1967).

-- Progress report French residue project. Mar. 13 (1968). HAZLETON, L. W.: Sampling and analysis for various pesticides in single samples

of citrus fruits. Proc. Intemat. Citrus Symposium, Riverside, Calif., Mar. 16-26 (1968). In press.

HEARTH, F. E., D. E. OTT, and F. A. GUNTHER: Oscillopolarographic analysis of Morestan residues in Valencia orange rind following thin-layer chromato­graphy. J. Assoc. Official Anal. Chemists 49, 774 (1966).

HINDIN, E.: Residue analyses in water resources. In G. Zweig (ed.): Analytical methods for pesticides, plant growth regulators, and food additives, vol. V, p. 90. New York: Academic Press (1967).

HOSKINS, W. M.: Methods for expressing the persistence of insecticidal residues on plants. Final report, Calif. contributing project to U.S. Department of Agriculture regional project W -45 (1961).

HULL, H. M.: A tabular summary of research dealing with translocation of foliar­applied herbicides and selected growth regulators. Weeds 8, 214 (1960).

ISHll, A.: Personal communication (Mar. 30, 1968). JASINSKI, R. J., and S. KIRKLAND: Analysis and distillation of propylene carbonate.

Anal. Chern. 39, 1663 ( 1967). JEPPSON, L. R., L. M. ELLIOTT, and F. A. GUNTHER: Persistence of residues of

Neotran on and in mature lemons and oranges. J. Econ. Entomol. 51, 914 (1958).

--, F. A. GUNTHER, and J. H. BARKLEY. Manuscript in preparation (1968).

118 F. A. GUNTHER

KLEIN, A. K.: Report on extraction procedures for chloro-organic pesticides. J. Assoc. Official Agr. Chemists 41, 551 (1958).

-- Determination of DDT in leafy vegetables. J. Assoc. Official Agr. Chemists 43, 703 (1960).

--, E. P. LAUG, and J. D. SHEEHAN, JR.: Extraction procedures for chloro­organic insecticides. J. Assoc. Official Agr. Chemists 42, 539 (1959).

LINSKENS, H. F., W. HEINEN, and A. L. STOFFERS: Cuticula of leaves and the residue problem. Residue Reviews 8, 136 (1965).

LYKKEN, L.: Important considerations in collecting and preparing crop samples for residue analysis. Residue Reviews 3, 19 (1963).

MELNIKOV, N. N.: Personal communication (Aug. 8, 1968). MENZIE, C. M.: Metabolism of pesticides. U.S. Department of Interior, Fish and

Wildlife Service, Bureau of Sport Fisheries and Wildlife, Washington, D.C., Special Sci. Rep't, Wildlife No. 96, May (1966).

MESTRES, R.: Pesticides in citrus fruits on the French market. Proc. Intemat. Citrus Symposium, Riverside, Calif., Mar. 16-26 (1968). In press.

METCALF, R. L., and R. B. MARCH: Behavior of octamethyl pyrophosphoramide in in citrus plants. J. Econ. Entomol. 45, 988 (1952).

--, T. R. FUKUTo, and R. B. MARCH: Plant metabolism of Dithio-Systox and Thimet. J. Econ. Entomol. 50, 338 (1957).

--, R. B. MARCH, and T. R. FUKUTo: Study of systemic insecticides: Location and amount of residue in plant tissues determined with aid of radio-phos­phorus tracers. Calif. Agr. 8(6), 5 (1954 a).

-- -- --, and M. G. MAXON: The behavior of Systox isomers in bean and citrus plants. J. Econ. Entomol. 47, 1045 (1954 b).

-- -- -- -- The nature and significance of Systox residues in plant ma­terials. J. Econ. Entomol. 48, 364 (1955).

MILLS, P. A.: Detection and semiquantitative estimation of chlorinated organic pesticide residues in food by paper chromatography. J. Assoc. Official Agr. Chemists 42, 734 (1959).

-- Paragraph 221 (A). In: Pesticide analytical manual, Vol. I. U.S. Department of Health, Education and Welfare, Food and Drug Administration, Washing­ton, D.C. (1965).

MUMMA, R. 0., W. B. WHEELER, D. E. H. FREAR, and R. H. HAMILTON: Diel­drin: Extraction of accumulations by root uptake. Science 152, 530 (1966).

MURPHY, R. T., L. K. GASTON, and F. A. GUNTHER: Colorimetric analytical method for Bidrin residues in alfalfa, celery, lemon peel, lettuce, orange peel, pota­toes, string beans, and tomatoes. J. Agr. Food Chem. 13,242 (1965 a).

--, J. R. O'NEAL, W. H. EWART, and F. A. GUNTHER: Persistence of Bidrin residues on and in mature oranges and in laboratory-processed citrus pulp cattle feed. J. Agr. Food Chem. 13, 550 (1965 b).

RAJZMAN, A.: Les residus de biphenyle dans les agrumes. Residue Reviews 8, 1 ( 1965).

SAMUEL, B. L., and H. K. HODGES: Screening methods for organochlorine and or­ganophosphate insecticides in foods and feeds. Residue Reviews 17, 35 (1967).

SCHNORBUS, R. R., and W. F. PHILLIPS: New extraction system for residue analysis. J. Agr. Food Chem. 15, 661 (1967).

SINCLAIR, W. B.: The orange: Its biochemistry and physiology. See especially chapter 9 by J. G. KIRCHNER, pp. 265 if. Berkeley: University of Califomia Press (1961).

SOUCI, S. W.: Biphenyl and o-phenylphenol as postharvest fungistats in citrus fruits and citrus products. Proc. Intemat. Citrus Symposium, Riverside, Calif., Mar. 16-26 (1968). In press.

Insecticide residues in citrus fruits 119

--, and G. MAIER-HAARI..ANDER: tl'ber den Diphenylgehalt und -geruch von Citrusfruchten und Citruserzeugnissen sowie den tl'bergang von Diphenyl auf unbehandelte Fruchte bei der Lagerung. Residue Reviews 16, 103 (1966).

STOBWASSER, H., B. RADEMACHER, and E. LANGE: EinHuss von Nachemtefaktoren auf die Riickstande von PHanzenschutzmitteln in Obst, Gemiise und einigen Sonderkulturen. Residue Reviews 22, 45 (1968).

STORHERR, R. W., and R. R. WATTS: Collaborative study of the ethyl acetate ex­traction, sweep co-distillation cleanup, ~nd GLC determination, using six parent organophosphate pesticides. J. Assoc. Official Anal. Chemists 51, 662 ( 1968).

SWISHER, H. E.: Personal communications (Mar. and Sept. 1968). THORNBURG, W. W.: Extraction and cleanup procedures. In G. Zweig (ed.):

Analytical methods for pesticides, plant growth regulators, and food addi­tives, Vol. I, pp. 87-108. New York: Academic Press (1963).

TuRRELL, F. M.: Tables of surfaces and volumes of spheres and of prolate and oblate spheroids and spheroidal coefficients. Berkeley: University at California Press (1946).

VAN MIDDELEM, C. H.: Principles of residue analysis. In G. Zweig (ed.): Analyti­cal methods for pesticides, plant growth regulators, and food additives, Vol. I, pp. 25-46. New York: Academic Press (1963).

-- Review of pesticides in Florida citrus and products. Proc. Intemat. Citrus Symposium, Riverside, Calif., Mar. 16-26 (1968). In press.

WEDDING, R. T.: Some physiological aspects of the use of systemic insecticides. J. Agr. Food Chem. 1,832 (1953).

WESTLAKE, W. E., and F. A. GUNTHER: Occurrence and mode of introduction of pesticides in the environment. Adv. Chem. Series 60, 120 (1966).

-- -- Advances in gas chromatographic detectors illustrated from applications to pesticide residue evaluations. Residue Reviews 18, 176 (1967).

WHEELER, W. B., and D. E. H. FREAR: Extraction of chlorinated hydrocarbon pesticides from plant materials. Residue Reviews 16, 86 (1966).

Wn.LIAMS, E. F.: Properties of O,o-diethyl O-p-nitrophenyl thiophosphate and O,O-diethyl O-p-nitrophenyl phosphate. Ind. Eng. Chem. 43, 950 (1951).

Wn.sON, C. W.: Personal communication (1950). WISNIEWSKI, J. V.: Pesticide residues in marmalades and preserves. F & M Facts

and Methods for Scientific Research 6(4), 3 (1965). ZWEIG, G. (ed.): Analytical methods for pesticides, plant growth regulators, and

food additives, Vols. I to V. New York: Academic Press (1963-1967).

Subject Index

A,B,C residues 52 Advisory committees, tolerance matters

9 Aldrin 44, 46, 65, 93, 94, 100, 101 - tolerances 11, 13 Allethrin, tolerances 11 Amino-parathion 69 Analytical integrity of extractives 92, 93 - integrity of samples 75 - methodology, citrus 74 ff. Analyzing residues in citrus samples 93

ff. Anthracene, half-life 40 Apparent residue values 4 Apples 12 Aqueous pathways 16 Aramite 38, 41, 43, 44, 46, 55, 56, 59,

64,67,76,90,92,94,97 - A,B,C curves 54 - degradation and persistence curves

18,19 - half-life 40 - residues, reduction by washing 60 - tolerances 10 Areas (surface) of citrus fruits 106 ff. - (surface) of citrus leaves 103, 106 ff. Arsenic tolerances 12 Attenuation curves 17 Azinphos methyl 37, 42-44, 46, 49, 50,

56,59,64,90,92,94,95,97,102 - methyl degradation and persistence

curves 18 - methyl, half-life 40 - methyl residues, reduction by

washing 59, 60 - methyl, tolerances 10, 13

Background variability 74,75,77 Benzene solutions of extractives,

storage 83 Benzopyrene, half-life 40 BHC 65, 93, 94 - tolerances 11, 12 Bidrin 37, 39, 43, 44, 46, 50, 64, 76, 90,

92,94,97,102 - degradation and persistence curves

19

- half-life 40 - residues, reduction by washing 60 - tolerances 10 BiphenyI5,57,77,78 Blending of citrus oils 56 Bromophos ethyl 94 Buttonhook peelers 81 ff.

Calcium arsenate 14 California-Arizona Citrus League

market survey residue program 64 ff.,99

California, residue-regulating legislation 6

Candied orange rind, residues in 42, 58 Carbaryl 41, 43-46, 49, 50, 52, 59, 64,

67,90,92,94,97,100-102 - degradation and persistence curves

20,21 - half-life 40 - residues, reduction by washing 60 - tolerances 10 Carbophenothion 37, 38, 44, 46, 65, 90,

93,94,97,101 - degradation and persistence curves

20,21 - half-life 40, 70 - multiple methods 70, 71 - tolerances 10, 13 Chlordane 39, 44, 46, 65, 67, 76, 90, 93,

94,97,100,102 - degradation and persistence curves

21 - half-life 40 - residues, reduction by washing 60 - tolerances 10, 11, 13 Chlorobenzilate 44, 46, 59, 65, 67, 69,

121

90,93,94,97,100,101 - half-life 40, 71 - multiple methods 70, 71 - persistence curves 22, 23 - residues, reduction by washing 60 - tolerances 10 Chlorothiophenol 70 Citral in citrus oils 56 Citrus "cream" 52 - extractives 6

122 Subject Index

- extractives, storage 92 - flavonoids 47 - fruit coring 81 ff. - fruit extraction 83 - fruit extraction solvents 85, 90, 91 - fruit mincing 83 - fruit peeling 81 ff. - fruit washing (see also Residue

removal by washing) 53, 58 - fruits 1 ff. - fruits, frozen storage 79 - fruits, growth dilution 75 - fruits, insecticide residues in 1 ff. - fruits, residue behavior 14 ff. - fruits, sampling intervals 75 - fruits, systemic insecticides in (see

also specific compounds) 59 ff. - fruits, tolerances 9 ff. - fruits vs. leaves, residues and

deposits 106 ff. - grove environment, residues in 102

ff. - juices (see also specific compounds)

5, 13,23,42 ff., 48, 61, 62, 80, 101, 104

- juices, insecticides in 44 - juices, oil contents 44 - juices, oil-free 42, 44 - juices, residues in 42 If. - leaves vs. fruits, residues and

deposits 106 If. - "milk"52 - molasses 42 - oil sacs 44, 52 - oils (see also specific fruits) 5, 13,

14,42 If., 48, 52 If., 96, 101 - oils as insecticide solvents 44, 47,

52,59 - oils, curing 52 - oils in juices 44 - oils, parathion in 56 - oils, preparation 52 - oils, residues in 52,55 If. - oils, solubility of pesticides in 85 - presampling considerations 74 ff. - products, commercial process for

manufacture 48 - products, insecticide residues in 1 ff. - pulp cattle feed (see also specific

compounds) 5, 6, 13,42,47 If., 74-76, 79, 101

- pulp cattle feed, moisture content 48,49

- pulp cattle feed, preparation 47-49 - pulp cattle feed, residues in 47 If.

- pulp, definition 42 - pulp extractives, preparation 74 ff. - rind extractives, preparation 74 ff. - rind, moisture content 49, 85 - samples,: -alysis 93 ff. - samples, processing 6, 79 If. - samples, storage 6, 78 - sampling procedure 76 ff. - trees per acre 102 - varieties, maturing seasons 80 - varieties and residues 41 Codex alimentarius 12 Codistillation with limonene 96 Cold-pressed citrus oils 52, 55 Credibility of residue data 39, 77 Cryolite 14 Cucumbers 12 Cuticular residues 53

DDD,seeTDE DDE 55, 65, 67-69, 93, 94, 100 DDT 2, 14,37-39,43-46,49,50,55-57,

59,65-69,90,94,97,100,102 - degradation and persistence curves

22,23 - half-life 40 - in dried citrus rind 58 - residues, reduction by washing 60 - tolerances 10-13 - vapor tension 104 Degradation curves (see also specific

compounds) 17-34,76-79,82,108 - curves, detailed 15 ff. - curves, typical 15, 16 - half-lives 16 Degrading residues 16, 17 Dehydrating solvents 83-85 Delnav, see Dioxathion Demeton 64,90,94,95,97, 101 - half-lives 40 - rate of transport 16 - residues in citrus fruits 59 ff. - sulfones 100 - thiol-isomer 59 - thiol-isomer, half-life in juice 62 - thiol-isomer, persistence curve 61,

62 - thiol-isomer residues in citrus 61 - thiono-isomer 59 ff. - thiono-isomer, half-life in juice 62 - thiono-isomer, persistence curve 61,

62 - thiono-isomer residues in citrus 61 - tolerances 10 Deposit, definition 3, 14, 15

Subject Index 123 - half-life 76 - vs. dosage relationships 36, 37 Deposits from e.c. vs. w.p. formulations

38 - on leaves vs. fruits 106 ff. - vs. dosages (see also Initial deposits)

37, 43, 106 ff. - vs. formulation (see also Initial

deposits) 38 - vs. residues 2 Developmental programs 99 ff. - residue data 4 Diazinon 38, 41, 43, 44, 46, 65, 67, 76,

90,92-95,97,100,102 - degradation and persistence curves

23 - half-life 40 - tolerances 10 Dibenzanthracene, half-life 40 Dibenzopyrene, half-life 40 Dichlorobenzilic acid 71 Dichlorobenzophenone 70, 71 Dichlorvos 94, 95 Dicofol 38, 43, 44, 46, 49, 50, 55, 56,

59,65-69,90,92-94,97,99,101 - half-life 40, 70 - multiple methods 70 - persistence curves 24, 25 - residues, reduction by washing 60 - solvent partition ratios 25 - tolerances 10 Dieldrin 44, 46, 55, 65-69, 90, 93, 94,

97,100-102 - A,B,C curves 54 - degradation and persistence curves

24,25 - half-life 40 - idealized residue behavior 15, 16 - tolerances 10, 11, 13 Dimethoate 44, 46, 50, 59, 64, 90, 92,

94,95,97 - degradation and persistence curves

25 - half-life 40 - residues, reduction by washing 60 - tolerances 10 Dinocap 65 Dioxathion 37, 38, 43, 45, 46, 49, 50,

64,66,67,69,90,92,94,97,99, 100, 102

- degradation and persistence curves 26,27

- half-life 40 - tolerances 10, 13 Disappearance curves 17

Dissipation curves 17 Di-Syston metabolites 34 DN-111 residues, reduction by washing

(see also DN compounds) 60 DNBP, tolerance 11 DN compounds (see also specific

compounds) 2, 14,49,50,59,64, 94,97

- compounds, tolerances 11 Dosages, citriculture 102 - of insecticides, California 99 ff. - then vs. now, citrus 97-100 - vs. residues 107 Dried citrus rind 5, 42 - citrus rind, residues in 58 Drift of pesticides 102 ff.

Economic poison, definition 6 Effective deposits 15, 16, 36, 53, 79 - deposits, definition 3 - residues 15, 16, 53, 79 - residues, definition 3 Emulsive vs. wettable powder

formulations, deposits 38 Endosulfan 64, 65, 67, 94 Endrin 64, 65, 67,93,94 Enzymes in citrus fruits 78, 79 EPN 45, 46, 64, 90, 94 - half-life 40 - tolerances 11 Ethion 38, 43, 45, 46, 49, 50, 59, 65, 67,

90,94,97,100 - degradation and persistence curves

26,27 - half-life 40 - residues, reduction by washing 60 - solvent partition ratios 27 - tolerances 10, 13 Exports and tolerances 11, 12 Extraction, definition 83 - solvents for residues, properties 6,

85 ff. Extractives storage 83, 84 Extracuticular residues 53 Extra-surface residues 58

Federal Food, Drug, and Cosmetic Act 6,7

- Insecticide, Fungicide, and Rodenticide Act 2, 6, 8

Fenitrothion 64, 65, 94 Field sampling 4 First-order reaction kinetics 16, 17 Flavedo 14 Florisil93

124 Subject Index

Fluorescence spectrometry 72, 73 Food Additives Amendment, see Public

Law 85-929 - additives, definition 7 - cutters 83 Fortification of extractives 84 French market survey residue program

64ff. Fruit surface area measurements 106 Fruit-to-fruit variations 78 Fruits vs.leaves, residues and deposits

106 ff.

Gallonages per acre, citriculture 102 Gas chromatography 57, 65, 69-72, 93,

95 Good agricultural pmctice 3 Grapefruit 5, 14, 41, 78 Grapes 12 Grove environment, residues in 102 ff. Guided samples 4

Half-life concept 34 ff. - concept, uses 34 ff., 39 ff. - definition 34 - values38 - vs. dosage 73 Half-lives of insecticides 39, 40 - of polynuclears 39, 40 Heptachlor 38, 45, 46, 58, 65, 67,90,93,

94,97, 100-102 - degradation and persistence curves

27 - half-life 40 - tolerances 10, 11, 13 Heptachlor epoxide 65, 67, 93 - epoxide, tolerances 11 HETP94 - tolemnces 11

Infrared spectrometry 70, 71 Initial deposits, difficulties in

establishing 36, 75 - deposits, factors affecting 15 - deposits, sampling for 36 - deposits, two bases 108 - deposits, value 36 Insecticides, dosages in California 99 ff. - half-lives (see also specific

compounds) 39, 40 - in juice vs. water solubilities 45, 46 - in the grove environment 96 - metabolites in citrus 101 - on leaves vs. fruits 96, 106 ff. - penetration into fruits 2 ff.

- residues in citrus fruits and products 1 ff.

- solubility in citrus oils 44, 47, 52, 59, 85

Juices, see Citrus juices

Kelthane, see Dicofol Kuderna-Danish technique 96

Leaching of soils 102 Lead arsenate 2, 14 - tolerances 12 Leaf areas, citrus 103, 106 ff. - areas, measurement 106 Leaves per citrus tree 103 - vs. fruits, residues and deposits 106

ff. Lecithins, removal 69 Legislation, California, for residues 6 - residue 6 ff. - residue, world-wide 9, 10 Lemons 2 ff. - moisture content 49 Lime-sulfur 2, 14 Liming opemtion 48, 49 Limonene96 - content of citrus oils 49 Lindane 58,65,67,94 - tolerances 11

Malaoxon 101 Malathion 45, 46, 49, 50, 55, 56, 59, 65-

68,90,94,95,98,99,102 - degradation and persistence curves

17,28,29 - half-life 40 - metabolites 34 - residues, reduction by washing 60 - tolerances 10, 13 Market-basket studies 3 Market residue data 5 - sampling 4, 5 - survey programs 4, 5, 64 ff. - survey residue data 64 ff. Marmalade 42, 101 - preparation 57 - residues in 57 Materials balance, citriculture 102 Mercury compounds, tolerances 13 Mermaid soap 60, 81 Mestres' procedure for citrus fruits 93 ff. Metabolite formation, time plot 34 Metabolites in citrus fruits (see also

specific compounds) 79, 96, 101 ff.

Subject Index 125

- in citrus juices (see also specific compounds) 45

Methodology, citrus 74 If. Methoxychlor 65, 93, 94 Methylcholanthrene, half-life 40 Methyl parathion 65,67, 94, 95 - parathion, tolerances 10, 13 Mevinphos64, 90,94, 95, 98, 101 - half-life 40, 62, 63 - residues in oranges 62, 63 - tolerances 10 Miller Bill, see Public Law 83-518 Mixed solvents for extraction 84, 85 Monitoring programs 4,42,65,66,74,

77, 96, 99 If. Morestan 49, 50, 59, 90, 92, 94, 98, 102 - half-life 40, 73 - multiple methods 72, 73 - persistence curve 28, 29 - polarography 73 - residues, reduction by washing 60 Muffins 58 Multiple methods 69 If., 101 - residue methods, citrus 69 If., 101

Naled 64, 90, 94, 95, 98 - tolerances 10 Naphthol from carbaryl 101 - in citrus pulp cattle feed 51, 52 - in citrus juices 45, 46 Neotran 41, 43, 45, 46, 64, 90, 94, 98,

102 - degradation and persistence curves

29 - half-life 40 - tolerances 10 Nicotine 14,90,94 - half-life 40 - tolerances 11 Non-aqueous pathways 16

Oil percentages of citrus fruits 14 Omite 41, 45, 46, 49, 51, 90, 92, 94, 98 - degradation and persistence curves

30,31 - half-life 40, 72 - multiple methods 71, 72 - residues, reduction by washing 60 Orange marmalade, residues in (see also

Marmalade) 57 - rind "bits" 59 - rind, residues in (see also specific

compounds) 58 Oranges 2 ff. - moisture content 49

Organohalogen compounds, see specific compounds

- values 69, 70 Organophosphorus compounds, see

specific compounds Ovex 39, 43, 45, 46, 53, 55, 59, 67, 90,

94,98,100,102 - A,B,C curves 53 - degradation and persistence curves

30,31 - half-life 40 - idealized residue behavior 15, 16 - residues, reduction by washing 60 - tolerances 11 OW-9 compounds 37, 41, 59, 91, 92, 98,

106 ff. - compounds, degradation and

persistence curves 31 - compounds, half-lives 40 - compounds, half-lives leaves vs.

fruits 106 - compounds on leaves vs. fruits 106 ff. - compounds, recoveries 106 - compounds, residues, reduction by

washing 60

Paraoxon 69, 100, 101 - in citrus juices 46 Parathion 14, 37, 41, 43, 45-47, 49, 51,

55,57,59,65-67,69,91-94,98-102 - degradation and persistence curves

32,33 - half-life 40 - in citrus oils 56 - in dried rind 58 - in grove air 103 ff. - in marmalade 57 - residues, reduction by washing 60 - residues vs. citrus variety 41 - tolerances 10, 12, 13 - ultraviolet absorption 105 - vapors in grove air 103 ff. - vapor tension 103, 104 Penetrated residues 15-17 Penetration, deposits and residues 2 ff. - of residues, hazard 2 Persistence curves (see also specific

compounds) 17-34, 69, 75, 77, 79, 96,101,102

- curves and citrus variety 41 ff. - curves, detailed 15 ff. - curves of related compounds 39, 41 - curves, typical 15, 16 - curves, uses 89 ff. - half-lives 76

126 Subject Index

Persisting residues 2 fl. Pesticide Chemicals Amendment, see

Public Law 88-518 - chemicals, definition 6 Pesticides, safety 8 - solubility in citrus oils 44, 47, 52, 59,

85 Petroleum oils, polynuclears in 40 - oils, tolerances 10 Phenthoate 94 Phosdrin, see Mevinphos Phosphamidon 64,67,91,94,95,98 - tolerances 10 Phosphatidyl cholines, removal 69 Photodecomposition 108 Polarography 72, 78 Polynuclears, haH-lives 89, 40 - in spray oils 40 Presampling considerations, citrus 74 fl. Press liquors 49, 52 Processed citrus products, tolerances 18 Processing of citrus fruits, How diagram

80 - of citrus samples 79 fl. Public Law 83-518 2, 5-7 Public Law 85-929 6 fl. Pyrethrins, tolerances 11

Quality assurance programs 4, 5, 65 fl., 77

Rag, citrus 18, 14, 44 Rainout 108 Random samples 4 Raw agricultural commodities 2, 6-9 - agricultural commodity, definition 6 Recommended dosages, citrus 5, 99 fl. Redistribution phenomenon 16 Reissuance phenomenon 16, 55, 59 Removal of residues by washing (see also

specific compounds) 58 fl. Residue alteration products in citrus 101 Residue-analytical methodology, citrus

4,74fl. Residue behavior, citrus fruits 14 fl. - biochemistry, origin 8 fl. - chemistry, origin 8 fl. - data, requirements 8 fl. - definition 14, 15 - half-life-concept 84 fl. - legislation, u.s. (see also specific

laws) 6 fl. Residue-life, 50 percent 34 Residue metabolites in citrus 101 - methods, multiple 69 fl., 101

- penetration 14 - penetration, hazard 2 - profiles, discussion 65 fl. - removal by washing (see also specific

pesticides) 8, 9, 14, 16,58 fl., 106 fl. Residues and citrus variety 41 - behavior 5 fl. - credibility 89, 77 - definition 8 - from market survey programs 64 fl. - in candied orange rind 58 - in citrus fruits and products 1 fl. - in citrus juices 42 fl. - in citrus oils 52 fl. - in citrus pulp cattle feed 47 fl. - in dried orange rind 58 - in grove environment 102 fl. - in marketed citrus 100 - in marmalade 57 - leaves vs. fruits 106 fl. - maximum and average (mean) 8-5,

68,69,75,78 - method specificity (see also Multiple

residue methods) 100, 101 - systemic insecticides in citrus fruits

(see also specific compounds) 59 fl. - vs. deposits (see also Deposits) 2 - vs. dosages (see also specific

compounds) 2, 18 fl., 85, 41, 106 fl. Rind and oil in citrus fruits 18, 14 - citrus, factors affecting thickness 18,

14 - percentages of in citrus fruits 14, 108 Rotenone 2,14 - tolerances 10 Ryania, tolerances 11

Sabadilla 14 - tolerances 10 Sample location, citrus fruits 77 - size, citrus fruits 77 - storage4 Sampling 4, 5, 75 - adequacy4 - for initial deposits 86 - harvested citrus fruits 77 fl. - procedures, citrus 76 fl. - sequences 76 - statistics 78 Schradan 48, 91, 94, 98, 101 - half-life in citrus 62, as - persistence curves 62, 68 - residues in citrus 62, 63 Seeds, citrus 18 Sevin, see Carbaryl

Subject Index 127

Snowout 103 Soil microorganisms 102 Solvents, dehydrating 83 - properties 85 ff. - residue extracting, properties 6, 85 ff. Spray mixture homogeneity 75 Stearoptenes 52 Storage of citrus extractives 92 - of citrus samples 78 - stability of extractives 92 ff. Stripping, definition 83 - solvents, properties 85 ff. Subcuticular residues 53 Subsamples of citrus fruits 81 Sulfur 2 - tolerances 10 Surveillance programs 4, 42, 66-67, 74,

77,96,99 ff. Systemic insecticides in citrus fruits (see

also specific compounds) 59 ff. - insecticides, rates of transport 16 - insecticides, stability in citrus juices

101 Systox, see Demeton

Tangerines 5 Tartar emetic, tolerances 11 TDE 37,39,57, 65, 67-69,91,93,94,

98,99,102 - degradation and persistence curves

32,33 - half-life 40 - tolerances 10 Tedion, see Tetradifon TEPP 91, 95, 98 - tolerances 11 Tetradifon 37, 45, 46, 49, 51, 55, 57, 59,

65,67,91,93,95,98,101 - degradation and persistence curves

33 - half-life 35, 36, 40, 71 - multiple methods 70, 71 - residues, reduction by washing 60 - tolerances 11 Thin-layer chromatography 72, 73 Time-decay curves 17

Tolerance concept 6 - definition 7 - petition requirements 8 Tolerances 2, 3, 5, 99 - and exports 11, 12 - Canada 9-11 - definition 3 - EEC 10,11 - establishment 7 ff. - exemptions from 7 ff. - for citrus fruits 9 ff. - for insecticides in citrus fruits 10, 11 - France 11 - Germany 9-11 - Italy 9-11 - Japan 11,12 - Spain 11 - The Netherlands 9-11 - U.S.A.7ff. - U.S.S.R. 10, 11 Tomatoes 12 Toxaphene 64, 65, 67, 93, 95, 98 - tolerances 10 Trithion, see Carbophenothion Triton X-IOO 62

Ultraviolet spectrometry 70, 71, 105 University of California recommended

insecticides for citrus 10-12 Usefulness of pesticides 7, 8

Vacuum concentration and residues 47 Vapors of pesticides 103 Volumes of citrus fruits 106 ff. - of citrus leaves 106 ff.

Washing of citrus fruits (see also specific compounds) 58 ff., 79

- to remove residues 58 ff., 79 Wax on citrus 16 - removal by washing, citrus 58 - replacement of surface, citrus 58 Wool 3 World-wide residue legislation 9, 10

Zero tolerances 8

Manuscripts in Press

Environmental decontamination of pesticide residues: Symposium, American Chemical Society, Special volume (No. 29).

Distribution of pesticides in immiscible binary solvent systems for cleanup and identification and its application in the extraction of pesticides from milk. By Morton Beroza, May N. Inscoe, and Malcolm C. Bowman.

Factors affecting the extraction of organochlorine insecticides from soil. By M. Chiba.

The problem of pesticide residues in Poland. By T. Stobiecki.