MARDI Res. l. 17(1) (1989): 55-68

Towards the development of an integrated pest management systemof Helopeltis in Malaysia

[. Azhar*

Key words: Helopeltis,Integrated Pest Management (IPM), cultural control, chemicalcontrol, biological control, ants, early warning system

AbstrakHelopeltis ialah perosak koko yang penting di Malaysia. Oleh itupengurusannya sangatlah penting untuk mendapatkan hasil koko yangmenguntungkan. Memandangkan koko ialah tanaman baru di Malaysiapenyelidikan dalam pengurtsan Helopeltis masih berkurangan. Kebanyakanpendekatan pengurusan perosak ini berpandukan pengalaman di AfrikaBarat, kerana banyak penyelidikan telah dijalankan di negara tersebut.Namun demikian, cara pengurusannya masih berasaskan kimia, yangmenjadi pendekatan utama dalam pengurusan Helopeltis di Malaysia.Perkembangan kawalan kimia dibincangkan.

Perkara-perkara utama dalam pengawalan biologi dan kultur jugadibincangkan. Kecetekan kefahaman terhadap prinsip-prinsip yangmerangkumi kaedah kawalan tersebut menyebabkan kaedah ini jarangdigunakan dalam pengurusan Helopeltis. Namun demikian, peranan utamasemut dalam mengurangkan serangan Helopeltis, terutamanya dalamekosistem koko dan kelapa patut diambil kira dalam menggubal sistempengurusan perosak bersepadu (PPB) untuk Helopeltis tidak kira sama adauntuk kawasan pekebun kecil ataupun ladang besar.

Sebagai matlamat utama untuk mengurangkan penggunaan racun kimia,pengawasan populasi Helopeltis dan kefahaman terhadap ekologinya telahmenjadi penting dalam pelaksanaan PPB. Penggunaan sistem amaran awaladalah salah satu cara untuk mencapai matlamat PPB dan seterusnyamempertingkatkan hasil koko.

AbstractHelopeltis is a major insect pest of cocoa in Malaysia. Hence its managementis of prime importance to ensure profitable yield. Cocoa is a relatively newcrop in Malaysia and research on the management of Helopeltis is relativelyscanty. As such, management approaches are largely based on West Africanexperiences where considerable research has been carried out. However, thismanagement approach is largely based on chemicals, which remain the firstline of defence in existing Helopeltis management strategies in Malaysia. Thedevelopment of chemical control of Helopeltis is discussed.

The salient features of biological and cultural control are also examined.A lack of understanding of the principles involved has resulted in minor use

*Cocoa and Coconut Research Division, MARDI Hilir Perak, P.O. Box 25,36307 Sungai Sumun, MalaysiaPresent address: MARDI, Cocoa Research Station, P.O. Box 324,91007 Tawau, MalaysiaAuthor's full name: Azhar Ismail@Malaysian Agricultural Research and Development Institute 1989

55

Development of IPM system of Helopeltis

of them in Helopeltis management. Nevertheless, the significant role of ants

in limiting Helopeltis attack, especially under the cocoa and coconut

ecosystem, is worth considering in the development of an integrated pest

management (IPM) system regardless of the size of cocoa areas.

With the ultimate aim of reducing chemical usage monitoring of the

Helopeltis populations and the understanding of -their ecology have become

important in the implementation of IPM. The use of an early warning system

is one of the means by which the objectives of IPM may be achieved with

subsequent improvement in cocoa yield.

IntroductionMirids are serious pests of cocoa. Theyare widespread throughout the cocoagrowing areas of the world, and about 40

species in the subfamily Bryocorinae (the

tribe Monaloniini and Odoniell ini) areknown to attack cocoa (Entwistle 1972).The tribe Monaloniini is the mostwidespread with the genus Monalonionexclusively feeding on cocoa in theneotropics. The species of Helopeltis aremore important in the Old World cocoagrowing areas. Attacks by members ofOdoniell ini occur mainly in the Ethiopianregion, Sabah and Papua New Guinea.Sahlbergella singularis (Hagl.) andDistantiella theobroma (Dist.) constitutethe two most damaging species of thistribe and are distributed mainly in WestAfrican cocoa areas (Entwistle 1972).

In Peninsular Malaysia, Helopeltistheobromae Mill. continues to be thegreatest concern of cocoa growers. It wasfirst reported attacking cocoa at theFederal Agriculture Experiment Station,Serdang in 1939 (Miller 1941). On theother hand, H. clavifer (Walk.) andPlatyngomiriodes apiformls Ghauri arethe two important mirid species in Sabahwith the former first discovered in 1957and the latter in 1962 (Conway 1971; Pang1981). However, mirid problems in Sabahare currently of secondary importancewith the discovery of the cocoa pod borer,Conopomorpha cramerella (Snell.), inlate 1980. Other mirid species present in

this region are H. antonii Sign. and FI.theivorq Waterh. in Indonesia

56

(Giesberger 1983) and H. bakeri Popp.and H. collaris Stal. in the Philippines(Entwistle 1972).

The biology of H. theobromae hasbeen descr ibed by Mi l ler (1941), Tan

$97aa) and Azhar (1986). No detailedbiological studies on H. clavifer areknown but a description of the life historyof P. apiformls was given by Pang (1981).Mirids are polyphagous, and H.theobromae, in addition to cocoa, alsoattack seven alternate host plants (Ahmadand Ho 1980). Smith (1978) reported 25alternate hosts of H. clavifer in PapuaNew Guinea but no report of alternatehosts for P. apiformis has been recorded.

Damage is primarily due to thefeeding of adults and nymphs on greenpods and young shoots or unhardenedstems. Platyngomiroides apiformn alsoattacks the chupon and fan branches aswell (Conway 1971; Pang 1981). Feedingby these mirids results in the developmentof circular lesions on pods and lenticularlesions on unhardened stems. Attacks onyoung cherelles may lead to cherelle wiltand complete loss of the crop may result ifthe infestation is severe. Infestation bythese mirids may also lead to subsequentattack by fungal pathogens. Correct croploss assessment attributable to Helopeltishas never been reported in Malaysiaperhaps because of the confoundingnature of contributory factors. However,a 257o decrease in yield due to miridinfestations was reported in Ghana(Stapley and Hammond 1959).

The recognition of the effect of miridinfestation on cocoa in Malaysia has led tothe institution of various control measuresagainst this pest soon after they werediscovered attacking cocoa (Miller l94l;Conway 1971). Since mirids are moreimportant in Peninsular Malaysia than inSabah, this review wil l emphasize themanagement of H. theobromae, althoughreference to other mirid species will alsobe made where appropriate.

Various management approaches toHelopeltis have been described andreviewed by a number of authors (seee.g., Mil ler 1941; Conway 1971;'Tanl9'l4b; Mainstone 1978; Azhar andJamaludin 1981; Azhar 1984, 1985, 1986).However, chemical control was and sti l l isthe most widely adopted approach bymany cocoa growers. The extensive use ofchemicals for the management ofHelopeltis is due to several reasons.Among them are quick action, easilyavailable and implemented and inefficientnatural control factors (Azhar 1985). Inthis review, it is therefore appropriate tolead the discussion with chemical controlfollowed by other control measures andeventually a discussion of theimplementation of an Integrated PestManagement (IPM) programme.

Chemical controlCocoa planting in Malaysia which beganin the early sixties, is relatively new whencompared to West Africa. Research onthe management of Helopelrls is relativelyscanty and many of the chemicals usedwere adopted from trial results in WestAfrica.

Historical viewIn West Africa, numerous controlmeasures with special emphasis onchemicals were tried against the cocoamirids since when they were recognized aspests in 1910 (Dundgeon 1910; Nichol andTaylor 1954). Spraying of trees withchemicals such as kerosene/soap

I . Azhar

emulsion, nicotine sulfate, and tar andpetroleum disti l late were tried with partialsuccess (Entwistle 1966). The subsequentuse of DDT. after World War II, bypainting branch unions or jorquettes andother mirids resting places provided bettercontrol (Coll ingwood 1971). The use ofHCH evolved after the chemical wasproved to be more successful than DDT incontroll ing cocoa mirids (Stapley andHammond 1959). The effectiveness ofHCH was attributed to its fumigativeeffect (Raw 1959). Since then, the use ofthis insecticide has become widespreadthroughout the West African cocoagrowing areas as well as other parts of theworld (Entwistle 1972; Omole and Ojo1981). However, the widespread use ofthis chlorinated hydrocarbon insecticideagainst cocoa mirids has resulted in thelocalized development of resistant strains(Dunn 1963; Entwistle 1964). Thephenomenon of insecticide resistance hasnecessitated continuous screening ofinsecticides for control of cocoa mirids inWest Africa (Prins 1965;Laryea 1967;Johnson eI al. 1970; Coll ingwood andMarchart 1971; Marchart 1971a, 1971b;Nwana et al. 1979; Omole and Ojo 1981;Owusu-Manu 1985).

The first attempt to control Helopeltiswas probably in Sri Lanka in 1907 wherethe spraying of sulfur and Macdonaghue'smixture proved a failure (Entwistle 1966).In Java, early attempts of insecticidalcontrol of cocoa mirids were made usingthe natural insecticide, derris and leadarsenate, but with l itt le success(Giesberger 1983). DDT was later used tocontrol Helopeltis in Java (Entwistle 1972).

The earliest report on the use ofinsecticides in Peninsular Malaysia tocontrol H. theobromrze was made byMiller (1941). He demonstrated thatdusting with pyrethrum-lime at weeklyintervals was effective in controll ing thepest. Lever (1949) found that threedustings of 0.5Vo DDT applied every 10days could check the damage caused by

57

Development of IPM system of Helopeltis

H. cinchonae Mann. and H' bradYi

Waterh. which were attacking the shoots

of tea bushes in the Cameron Highlands.

The earliest report on the use of

insecticide to control cocoa mirids in

Sabah was in 1959 when HCH dust was

applied to the young growing points of

cocoa trees (Conway 1971)' Further

reports on the development of insecticide

usage against cocoa mirids in Sabah did

not appear unt i l the sevent ies.

Current situationInsecticides Spurred by the significant

results of mirid control in West Africa

using HCH, this chemical was and is sti l l

w idely used by many cocoa growers in

Peninsular Malaysia. However, because

of the reported development of mirid

resistant strains and the suspected tainting

effect through extensive use of HCH,

alternatives to HCH were sought. The

Department of Agriculture recommended

the use of other chemicals including

dieldrin and trichlorphon for Helopeltis

contro l (Anon. 1977). However, d ie ldr in

is no longer recommended because of its

h igh mammal ian tox ic i ty . Otherinsecticides such as chlorpyrifos and

methamidophos, though not officially

recommended, were also used bY a

number of cocoa growers (Azhar 1985).

Screening efforts by Jamaludin (1981) and

Lee et al. (1986) further added to the l ist

of suitable insecticides for Helopeltiscontrol and include the carbamate and

synthetic pyrethroid groups. A l ist of

insecticides currently recommended for

used against Helopeltis in Peninsular

Malaysia is given in Table l.

Application methods Variousinsecticidal application methods are

employed, some of which were reviewed

by Khoo et al. 1983. Growers may use

methods ranging from dusting, spraying

and fogging depending on the severity and

distribution pattern of the infestation, the

phenology of cocoa crops and the

58

Table 1. Some of the commonlY used

insecticides in Helopeltis control

Common names Group

Gamma-HCH ( l indane)

PropoxerDioxacarbCypermethr inAlphamethr in

Del tamethr in

organochlorinecarbamatecarbamatepyrethroidpyrethroidpyrethroid

economlc constra lnts .Dusting with gamma-HcH dust has

been recommended in the Past in

Peninsular Malaysia (Anon. 1977) but the

method is now obsolete. The method was

also recommended for mirid control in

Papua New Guinea (Smith 1979).

Spraying is the most widely practised

method of applying insecticides against

cocoa mirids and the operation may be

carried out using manual knaPsacksprayers or portable motorized mist

blowers. The manual knapsack sprayers

are suitable where cocoa trees are not too

tall whereas mist blowers are more

suitable for taller trees in order to reach

pods in the upper canopy (Taylor et al.

1982). The manual knapsack sprayers are

more popular among smal lholdersbecause of the small acreage and their

l imi ted resources whi le many p lantat ions

use the motorized mist blowers as well as

manual knapsack sprayers.Comparat ive ly , the motor ized mist

b lower has a h igher work ing rate than the

manual knapsack sprayer (Taylor et al.

1982). A worker can cover only 2-3 ha/

day using the knapsack sprayer comparedto the 5-6 ha/day us ing the motor ized

mist b lower. At the same t ime, the

manual knapsack sprayer is a high volume

application method compared to themotorized mist blower which is low tomedium volume. Hence, larger amountsof insecticides are applied per unit area

using the former sprayer.Fogging is commonly used when

greater coverage of insecticide is required

and labour is l imited. The operation may

be carried out using portable pulsejetfoggers when the in festat ion is notwidespread or tractor-drawn pulsejetfoggers when larger outbreaks occur(Taylor et al. 1982). However, fogging issuitable for use with insecticides having afairly high degree of thermostabil ity andonly on mature cocoa with a closedcanopy. The use of insecticides havingfumigative effect is an added advantage.

Localized treatment of infestation isencouraged because of the heterogenousdistribution pattern of Helopeltis in thefiefd (Conway 1971; Tan 1974a; Wills1986). In this situation, knapsack sprayersand mist blowers are commonly used.Taylor et al. (1982) reported that portablepulsejet foggers may also be useful forspot treatment, as the application cost isonly one-fourth of that of knapsacksprayers or mist blowers. During outbreaksituations, the larger pulsejet foggerscould provide more rapid coverage andbetter bioefficacy than knapsacks or mistb lowers. When fogging equipment is notavailable, spraying with chemicals havinga strong fumigative effect at every secondor more row of cocoa trees may bepractised. This method has been practisedin Papua New Guinea (Smith 1981).

Interval and timing ofappfication ITektpeltis populationbuild-up occurs at diff 'erent t imes of theyear with the trend being dictated by theavailabil ity of food, breeding sites, andweather (Tan 1974a; Azhar et al. 1983;Azhar 1986). Since the populationincreases when pod numbers are high andafter the onset of the rainy season, controlof the pest may be achieved throughapplication of insecticides during theperiod of increasing pod numbers andascending rainfall (Tar 1974a; Azhar1986) or during the preceding dry season(Azhar 1986). Dry season spraying hasbeen recommended in Nigeria and hasbeen found to delay and reduce the build-up of mirid populations (Youdeowei

I . Azha r

1970). As the objective of a sprayingprogramme is essentially to protect thedeveloping young cherelles, such aprogramme that coincide with thisparticular period is appropriate. In anycase, each spraying programme wouldessentially consist of twc sprayapplications about 18-27 days apart(Azhar 1986; Wi l ls 1986), wi th the la terapplication aimed at destroyingindividuals that emerged from eggs thatwere protected during the earlier spray(Entwistle 1972 Azhar 1986).

Proper application timing during theday is another factor that determines theef lect iveness of the spraying programme.Based on a study of the daily activitypattern of H. theobromae, Azhar (1986)suggested that spraying or fogging is moredesirable in the early morning or earlyevening as more individuals are exposedduring these periods. However, otherfactors such as practicality and weathercondi t ions may inf l uence appropr ia letiming.

-faylor et al. (1982) reported that

the effectiveness of fogging was enhancedwhen appfied during 1930-2234 h as therise of fog was suppressed by temperatureinversion conditions durins these hours.

Cultural controlSome cul tura l pract ices in cocoaproduction have become established thatthey may not be considered a part of thetotal pest management package. Theseinclude such practices as the managementof shade level, pruning and the planting ofresistant varieties.

Management of shade levelThe role of shade in the management ofHelopekis is debatable. To date, noquantitative studies have been made toascertain the role of shade in themanagement of Helopelrrs in Malaysiaexcept for isolated observational reports.Helopeltis is a shade-loving insect, thatprefers areas with well-developed closedcanopies which afford protection from the

Development of IPM system of Helctpeltis

sun, heavy rain, and strong wind; orareas wi th h igh humidi ty (Mi l ler 1941;Azhar and Jamaludin 1981). Smith(1979), in h is rev iew on theinterrelationship between shade types andpest problems in Papua New Guinea,stated that mirid population can bedamaging under a nil or short shaderegime but less troublesome under thetaller shade types. In West Africa, miridinfestation can be particularly damagingwhere there are gaps or breaks in theshade tree canopy or where overheadshade is sparse (Wi l l iams 1953; Entwist lere72).

In Malaysia, however. no obviousrelationship could be established betweenshade types and Hebpehis attack asinfestations occur regardless of whethercocoa is planted under coconut orGliricidia. Nevertheless, the incidence ofHelopeltis attack was observed to be lessin cocoa planted under taller shade regime(such as under tall coconut of more than40 years old) than those planted undershorter shade regime (such as under dwarfand semi-dwarf coconuts or under heavyshade of Gliricidia). This phenomenoncould possibly be due to the more exposedenvironment under tall shade regimeleading to less moisture retent ioncapacity, greater exposure to sunlight andbetter aeration as compared to the lowand heavy shade of cocoa monocultureunder dwarf and semi-dwarf or Gliricidiashade. Under the latter conditions. thegreater intensity of the green house effecttends to provide a relatively warm andmoist atmosphere suitable for Helopeltisto flourish. Conversely, Lim (1978)observed that removal of shade in amonoculture cocoa in Sabah led to anincrease incidence of infestation by miridsand other insect pests. Accordingly, norecommended general policy on themanagement of Helopelrrs through shademanipulation could be established.

Resistant clonesResearch effort on this aspect of pestmanagement of Helopehis in Malavsia isscanty. The reasons for the lack of s tudiescould be due to the perennia l nature ofcocoa and the heterogenous infestation ofltelopeltis in the field. Currently. thereare no recommended c lones which are lesssusceptible to Helopeltis but research is inprogress to indentify clones which are lesssuscept ib le to th is pest through v isualassessment (Azhar 1984). Elsewhere,l imited amounts of research on thesusceptibil i ty of clonal cocoa to miridshave been reported in Ghana (Posnette19,13), Cameroon and lvory Coast(Decazy and Lotode 1975; Decazy andCoul ibaly 1981) and Papua New Guinea(Smi th and Mo les 1981 ) .

Hand collection and scorchingThis method of Helopeltis control hasbeen pract ised s ince the beginning of th iscentury in Indonesia (Giesberger 1983).Hand collection of both adults andnymphs is made using a spl i t bamboost ick, wi th one end d ipped into somest icky f lu id. Zehntner (1903) emphasizedthat the operation should be carried outwhen Helopelrls populations are low tcrprevent a rapid increase in the nextgenerat ion. Especia l ly in the largerplantat ion sector in Malaysia, th is methodof Helcpeltis management is unrealisticbecause of t ime and labour costs.However, i t may be usefu l tosmal lholders.

Because manual co l lect ion is t imeand labour in tensive, scorching ofHelopeltis on mature pods with fire wasrecommended in Indonesia particularlyduring the high population period(Giesberger 1983). However, th is methodwas not popular and was discardedshortly. In Malaysia, scorching has neverbeen recommended at all because it isimpractical.

60

Biological controlParasites and predatorsLitt le is known of the biological control ofHelopeltis by parasites and predators. Upto the present no parasite has ever beenrecorded attacking H. theobromaealthough three species of egg parasites,namely Anagyrus sp. (Hymenoptera:Mymaridae), Erythmelus helopeltisGahan (Hymenoptera: Mymaridae) andTelenomus sp. (Hymenoptera:Scelionidae), have been reported toattack 11. cinchonae on tea in Camerontlighlands (Ahmad and Ho 1980). In Javaa braconid parasite, Leiphron helopeltidisFerr., with its hyperparasite, Stictopisthusiavensis Ferr.. was recovered fromH. antonii nymphs (Giesberger 1983).Attempts at releasing the parasiteL. helopehidls were made in Indonesiabut were discontinued due to itsinef fect iveness. An egg parasi te.Telenomus sp. (Hymenoptera:Scelionidae), and a nymphal parasite.Euphorus helopeltidis (Hymenoptera:Braconidae), have been recordedattacking S. singularis and D. theobromaein West African cocoa with an averageparasitism of 25% and 12Vo in Ghana andNigeria respectively (Entwistle 1972).

The nymphs of Helopeltis spp. inIndonesia have also been reported to beattacked by two species of mermithidnematodes, Hexamermis microamphidisSteiner and Agamermis paradecaudataSteiner, with parasitization ranging from5-10% (Giesberger 1983). Pathogenicfungi such as Beauvaria, Hirsutella andAspergillus were occasionally recordedparasitizing cocoa mirids in West Africa(Coll ingwood 1911).

Many predators have been observedto have the potential of attackingHelopeltis in the field. A species ofreduviid. Cosmolestis picticeps Stal., hasfrequently been encountered but itsimportance is not known (Azhar 1985).This species together with the others,Sycanus leucomesus Walk., Isyndus heros

L Azhar

F., Euagoras plagiatus Burm., andRhinocoris marginellus Thunbg. havebeen mass-bred and released in CameronHighlands for the control of Helopeltis ontea (Corbet and Pagden 1941). However,the resul t o f the re lease is not known.Conway (1971) also reported the presenceof three of these reduviid species in Sabahbut did not describe their significance.Spiders were also observed to attack bothadults and nymphs of Helopeltis in thef ie ld (Azhar 1985).

AntsAnts are the most abundant insect in thecocoa ecosystem. The dominant speciesare generally distributed in a mosaicpattern as a result of intense interspecificcompetit ion and the influence of l ight andshade regimes (Leston 1971,1973a,1973b; Room 1971; Majer 1972. 1976a,1916b Bigger 1981; Jackson 1984). Thei rrole as a control agent of insect pests hasbeen rev iewed bv Clausen (1940) andRoom (1973). The use of ants as abiological control agent against cocoamir ids was real ized in the ear ly par t of th iscentury when cocoa growers in Indonesiadeliberately introduced the indigenousblack ant, Dolichoderus bituberculatusMayr into the cocoa fields to controlHelopeltis (Giesberger 1983). Perhaps themost extensive investigations on theecology and role of ants in l imiting cocoamirids have been carried out in WestAfr ica (see e.g. , Leston 1971,1973a,1973b: Coll ingwood 1971 ; Room 1971 ;Majer 1972, 1976a, 19'l6b; Taylor 1977,1978; Jackson 1984). Control of cocoapests by ants have also been developed inPapua New Guinea (Room 1973; Smith1981). In Malaysia, the importance of antsin controlf ing Helopeltis was mentionedby Conway (1971) and Mainstone (1978)who referred to the successful Indonesianexample. Azhar (1985) reported the antspecies composition and briefly discussedtheir roles in the cocoa ecosystem.

In West Africa, although numerous

6 1

Development of IPM system of Helopeltis

Table 2. Ant species (Hymenoptet:a: Formicidae) col lccted from cocoa growing areas in

Pcninsular Malaysia (After Azhar 19t35)

D o lic ho de rus tho r ac ic us Smith

Dolichoderus sp. (thoracicus - gp.)

Crematogaster ( Acrocoelia) sP.

Crematogaster sp.

Meranoplus sp.

Tetraponera rufonigra (Jerdon)

Tetraponera sp.

Anoplolepis longipes (Jerdon)

O do nto mac hus s imi llim us SmiIh

Odontomachtts rxosus Smith

Odontomachus haematodes L.

Diacamma regosum (l-e Guillon)

Technomy rme x,r/b?e.t (Smith)

O e c o p h1: lla s m ar a gdina (F ab.)

Solenopsis geminata F.

Pheitlole sp.

Camponotus (Tanaemyrmex) rnconspicous N4ayr

Camponotus gigas

Camponotus sp.

M yopopone castanea (Smith)

Tetramorium pacificus Mayr

Iridomyrmex sp.

Paratn rhina lttngicornis (Latr.\

Paratrexhina sp"

O donto ponera tronsv erso (Smith )B othroponera trid entzta (Smith)

Brachyponera sp.

Hypoponera sp.

Anochaetus sp.

Cerupach,vs sp.

Pachl-cond1,la sp.

Leptogenys sp.

Pheidologenton sp.

Poly rhachis /eavlssirna Smith

P o l,- r hac hi s tlblalls Smith

Polyrhuchis thrinax Roger

Polv rhac hi s ft ector Smith

P ol,- rhac his blcolor Smith

P o Iy r hac his riir'e.sr Smith

Polyrhachis sp.

Moncmorium sp.

Trachymesopus sp.

ant species are known in the cocoaecosystem, only a few are dominant and

are noted for their important role in

limiting mirid attacks. Among the 52

species l isted by Majer (1976) species in

the genera Oecophylla, Crematogasterand Macromischoides are the mostcommon. Although earlier evidence is

somewhat conflicting (Will iams 1954), thepresence or absence of the cocoa mirid

D. theobroma are known to be largelY

influenced by the presence and absence of

one of these dominant ants (Majer 1972).

Both O eco phy lla and M ac r omis c ho ide sprey on D. theobroma and S. singularisand excfude Crematogaster but neither

have been reported to tend mealybugs(Leston 1973a). These two speciestogether have been reported to confer

adequate protection on 657o of matureand healthy trees (Leston 1973b) althoughCollingwood (1911) provided a moreconservative figure of only 15.Zc/o.Attempts at artif icially spreadingOecophylla in Ghana has not beensuccessful. Coll ingwood and Marchart(I971) attributed the failure to the relative

stable colonies of the Oecophvllo. which

forage mainly on l itter. Although theimportant South American ant speciesWassmannia auropunctata Roger has been

reported to give good control of cocoamirids, the ants failed to spread outsidethe area of original introduction (Mire

1910).Successful control of Helopeltis has

been reported in Java by introducing D.

biturberculalas into cocoa plantationsprovisioned with artif icial nests of driedbanana and cocoa leaves (Giesberger1983).

' Ihe success of th is contro l depends

ent i re ly on the avai labi l i ty of themealybug, Planococcus l i lacinus (Cockl. ),which provide the ants with honey-dew. It

has been detnonstrated that Helopeltispopulations were controlled for over 40

years by maintaining large populations of

an ts and mea lybugs . Van de r Goo t (1917 )

reported that increased mortality was

observed in mealybugs unattended by theblack ants as opposed to those tended by

ants. Currently, in Indonesia biologicalcontrol by using ants has stopPed.

In Malaysia, Azhar (1985) l isted 43

species of ants collected from the cocoa

ecosystem (Table 2). Only a few were

62

Table 3. Potential ant species as biologicalcontrol asents of Helooeltis

Species Subfarnily

Dolic hoderus thoracicusOecophylla smaragdinaAnaplolepis longipes

Crematogaster spp.

Dol ichoder inaeFormicinaeFormicinaeMyrmicinae

observed to have potential in controll ingHelopeltis (Table 3). Among these speciesonly Dolichoderw thoracicris Smith seemedto be effective against Helopeltis. T\isspecies is predominantly found in thecocoa-coconut ecosystem where it formsnests mainly in the coconut crown (Azharand Musa 1988). It sometimes buildtemporary nests in the cocoa canopy or inthe dried leaf litter on the ground and oftenwith a trail leading to the main nest. Thebeneficial effect of this species is due to itsmutualistic relationship with a few speciesof mealybugs (e.g. Cataenococctts hispidru(Morr.), P. lilacirun and P. pacificus Cox)which infest mainly cocoa pods and youngshoots. The maintenance of largepopulations of these ants, which aremainly arboreal, in the cocoa plantationsmay be achieved by providing additionalmigrating alleys from their nests in thecocoa canopies using materials such asfallen coconut fronds. Proper shade levelsuch as the complete canopy of cocoatrees should be maintained to ensure thebuild-up of mealybug colonies as theythrive in well-shaded fields. Although themealybug populations may occasionallyget excessively high, the populationswould normally decline as a result ofdispersal and mortality infl icted byvar ious natura l enemies (Azhar 1985).The use of the black ant-mealybugassociation to control Helopeltis is onlyfeasible where cocoa is interplanted undercoconut. It may not be feasible inmonoculture situations because black antsdo not thrive well probably due to the lackof nesting places. In addition, competit ionpressures impose by other ant species mayaffect the black ant in this ecosvstem.

I. Azhar

Other ant species that seem toprovide some Helopeftis control areO e co p hy lla smaragdina F ab., Ano p I o le p islongipes Jerd. and Crematogaster spp.Oecophylla smaragdina does not spreadvery fast and they seem to acquire theirfood items on the ground. The problemwith using A. longipes to controlHelopeltis is its superior competitive effectthat may drive other ant species out of thecocoa field, and its sporadic behaviour invisiting the mealybugs. Crematogasterspp. mostly forage or tend mealybugsinside their galleries on the branch and,therefore, any intruder on the pods maybe ignored. The association of mealybugswith other ant species such as Meranoplussp. may be accidental and thereforerender l itt le or no effect in deterrinsHelopeltis attack.

Use of pheromoneThe presence of an attractant pheromonein H. clavifer has been reported by Smith(1917) in Papua New Guinea. InMalaysia, caged virgin females ofH. theobromae has been observed toattract adult males in the fields indicatingthe presence of sex attractant (Azhar1982, unpublished data). Although therewere no further investigations on thisaspect there are certainly prospects ofincorporating pheromones in theH elopeltis management programme inMalaysia, especially as a usefulmoni tor ing tool .

The integrated pest management systemThe evolution of pest managementstrategies for Helopeltls in Malaysia hascentred entirely on the use of chemicals.However, over reliance on chemicals hasbeen shown to be environmentally andeconomically unsound (Conway 1969;Azhar 1985). Unexpected problems suchas outbreaks of secondary pests mayappear following unjustified chemicalapplications. Although insecticideresistant strains of H. theobromae have

63

Development of IPM system of Helopeltis

not been detected in Malaysia (Dzolkhifli

et al. 1986) its eventual development may

lead to a situation of 'pesticide treadmill'(van den Bosch 1975). There is no

denying that chemicals have an important

role in the management of Helopeltis but

they have to be harmoniouslyincorporated into an integrated pest

management (IPM) system to ensuremaximum economic benefits with minimal

costs incurred. IPM is a dynamic system

and may be adjusted accordingto variations in cocoa cultural practices or

to incorporate any new informationgathered peiiodically from field research.

In Malaysia, cocoa is either planted as a

smallholder's crop of minimal acreage or

as a plantation crop with areas of more

than 100 ha. In addition, cocoa may beplanted either as an intercrop undercoconut or as a monoculture underGliricidia shade. Each of these planting

systems certainly influences themanagement strategies of Helopeltis as

the environmental variables within each

system will differentially affect the

ecology and behaviour of Helopeltis.However, the following underlyingelements of IPM as listed by Flint and van

den Bosch (1982) do not vary:

o Decision maker, in this case eitherthe owner or the manager

O Knowledge or information about thepest

o Sampling or monitoringo Decision making criteriaO Management tactics

Detailed elaboration of these elementswere given by Flint and van den Bosch(19U) and Smith (1983). Examples ofsuccessful implementation of IPM againstHelopeltis are provided by the system ofmirid control practised in the Lubolelaplantation in the Congo Republic(Entwistle 1972), Pabatu Estate in North

Sumatra, Indonesia (Youdeowei and

Toxopeus 1983) and Dunlop Sagil Estate,

Johore (Wills 1986).

64

Implementation of the IPM programme

The IPM system can be implemented by

both estates and smallholdings. However,the smallholders may not have aselaborate a system as the estates sincetheir resources are rather l imited. The key

to the development of this approach ismonitoring with the ultimate objective of

reducing the amount of chemical usage.

Blanket spraying is common amongsmallholders regardless of pest status.This is because smallholders are normallyignorant or have litt le information aboutthe pest. At the same time the small areaof the holding may be completely infestednecessitating blanket spraying. However,

the management system may be improvedif the grower carries out regularmonitoring to ensure that chemicalapplication is applied at the correct t imeto achieve increased effectiveness andreduce the frequency of chemicalapplication. Weather pattern andcropping phenology should also beconsidered in deciding chemicalapplication. It has been found in various

studies (Tan 1974a; Azhar 1986; Wills1986) that the best t ime to apply chemicalsis when there is maximum build-up ofHelopeltis which coincide with ascendingrainfall and increasing pod numbers. Spottreatment of only the infested trees couldspare some of the beneficial insectsavailable within the holding. Althoughthis approach is slightly laborious it maybe compensated by the small size of theholding. The availabil ity of black ants,especially under the cocoa-coconutecosystem, further necessitates spottreatment. Nevertheless,the effectivenessof this management system may not belasting due to the immigration of breedingadults from the surrounding, unmanagedholdings. As such, the institution of aregional approach to Helopeltis

management is often necessary to achievepersistent effectiveness which iseconomically and environmentallyjustifiable. This requires cooperative

efforts from all growers within the region.In the estate sector, pest

management system is often betterimplemented than in the smallholdersector. Here, pest and disease situationsare routinely monitored and infestationsare promptly treated. The treatmentmethods, whether fogging, spot treatmentor blanket spraying depend on theseverity of infestation. Since monitoring ismainly on the basis of detecting thepresence or absence of damage, thedetection of damage is occasionally lateleading to heavy chemical application tosuppress the high population causing thedamage. As such, the system is alsoinefficient in terms of cost-effectiveness.This leads to the development of amanagement using the Early WarningSystem (EWS) or Early Response System(ERS).

Early warning systemThis approach was initiated and practisedin a North Sumatran cocoa estate(Wignyosoemarto and Soebiyakto 1980;Youdeowei and Toxopeus 1983). The useof this system in Malaysia is as recent as1986 when Wills reported the adoption ofthis system at the Dunlop Sagil Estate,Johore. Basically, the objective of thisapproach is to reduce the amount ofchemicals used without reducing itseffectiveness. In this system the areas ofinfestation or aggregation of Helopeltisare located and treated in the early stagesof population build-up limiting theoutbreak. The development of this systemtakes into consideration various factorsinvolving the biology of Helopeltis, suchas the rapid build-up of its population(Youdeowei and Toxopeus 1983), itsaggregation behaviour (Wills 1986) andthe condition of the cocoa canopy(Youdeowei and Toxopeus 1983). Azhar(1986) also suggested the incorporation ofthe crr:pping cycle or pod numbers andweather patterns, especially rainfall, aswell as consideration on the existing status

I . Azhar

of the naturally occurring biologicalcontrol agents, such as ants, in thissystem.

The organization of this pestmanagement system has been outlined by(Wignyosoemarto and Soebiyakto 1980;Youdeowei and Anwar (1983) and Wills(1986). Generally, the total cocoa area isdivided into sections or blocks ofproportionate size which are thensubdivided into plots of 5 ha (Figure 1).Monitoring is carried out within subplotsconsisting of an appropriate number ofcocoa trees to allow for satisfactoryidentification of aggregations as used byWills (1986). A subplot consists of a groupof four trees distributed evenly at 5.5groups per hectare. Wills (1986) carriedout monitoring at 18 days interval as thelife cycle of Helopeltis from egg to adult isabout 21 days. He also secured the actualnumber of Helopeltis at a hand heightusing a scoring system of 1 to 5; a score of1 indicates one insect, 2 indicates two, andso on but a score of 5 indicates that five ormore than five insects have beenrecorded. He advocated immediatechemical treatment only to subplots andadjacent plots with a score of 3 to 5.However, he did not take intoconsideration the presence of ants (suchas their distribution) as a natural control

Figure I. Implementation procedures of EWS.Demarcation of the area into main plots of 5 haeach (A) and establishment of subplot (B)where sampling will be carried out onpredetermined number of trees

65

Development of IPM system of Helopeltis

agent in the cocoa field although they are

known to provide some control of

Helopeltis in the field (Azhar 1985).

The use of this sYstem has been

demonstrated to reduce the amount of

insecticide and labour required in addition

to a reduction in yield loss due to

Helopeltis (Youdeowei and Toxopeus

1983; Wills 1986). Wills (1986) indicated

that only 57o of the total area at each

inspection round required treatment. In

North Sumatra, Youdeowei and

Toxopeus (1983) reported the use of

chemicals was reduced by 50Vo through

the implementation of this system. As a

result of the reduction in insecticide usage

through spot treatmerrt, the ecology of the

ecosystem is maintained and the natural

enemies spared. In addition, the

establishment of this system allows for the

monitoring of other aspects of cocoa

growing such as diseases and crop level.

As problems are uncovered appropriate

remedies can be immediatelYimplemented.

AcknowledgementsI am grateful to Dr Richard Zack,

Department of Entomology, Washington

State University and two anonymousreviewers for their helpful comments to

improve the manuscript. This paper was

originally presented at the 2nd

International Conference on Plant

Protection in the Tropics, Kuala Lumpur,

March, 1986.

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Accepted for publication on ll May 1988

68