8/12/2019 j.desal.2011.08.061

1/1

For personal use. Only reproduce with permission from Elsevier Ltd.

One of the absurdities of organic foodism is that growersspray their crops with pesticides such as copper sulphate(CuSO4)a thoroughly poisonous (and inorganic)substanceyet reject modern, safer, thoroughly researchedalternatives. Organic farmers are so attached to coppersulphate that they won the right to continue using it despite aEuropean Union ban originally scheduled to come into effect2 years ago.

CuSO4 was long since removed, on safety grounds,from childrens chemistry sets. It is persistent in the soil,and is a hepatotoxin that has caused documented cases ofliver damage in vineyard workers.Nevertheless, organic farmersdeploy it on their fields in theinterests of naturalness. Strange.

Its the inconsistency thatconcerns me here, not theagricultural use of copper sulphateper se. In the real world, thissubstance has been a tremendousboon, particularly when mixed

with lime (calcium hydroxide)as Bordeaux mixture to controllate potato blight caused byPhytophthora infestans (the agentof the Irish potato famine).Present-day replacements, deridedby the organic movement, areboth more effective than CuSO4and less toxic to non-targetspecies. But in its day agriculturalcopper was a lifesaver.

The man who made it so wasPierre Marie Alexis Millardetwho, as Peter Ayres says in an

appreciation (Mycologist 2004; 18: 23), could have been asfamous as Petri or Bunsen had he been more pushy andappended his name to his innovation. Among Bordeauxmixtures many attractive features, it has not triggered theemergence of resistance among plant-pathogenic fungi and ithas remained relatively cheap.

Millardet was born in 1838 in a small town in the Jura,France, not far from Louis Pasteurs birthplace. He studiedmedicine in Paris, where he developed an interest inmedicinal plants and became a member of the SocieteBotanique de France while still a student. Thence toGermany, where he studied initially under WilhelmHofmeister, the first person to discern the alternating

generations of mosses, ferns, and other plants, and then underthe distinguished mycologist Anton de Bary.

After serving in the Franco-Prussian war, Millardet tookup a professorship in Nancy and was soon asked to visit thewine-producing region of Bordeaux whose vines were beingthreatened by phylloxera infestation. It was here, during the1870s and 1880s, that Millardet had the insight to recognise,and prove scientifically, that a mixture of copper sulphate andlime might be exploited as a fungicide against mildew andother conditions.

Others had made claims for both substances (and somevineyard owners had painted maturing vines with coppersulphate to deter thieves). But as Ayres points out, it was

Millardet who took the greatstep forward, who by experimentperfected a fungicide which couldbe applied to foliage withoutdamaging either a plant or itsfruits.

Helped by Ulysse Gayon,professor of chemistry atBordeaux, the mycologistworked out pragmatically the

most effective concentrationsand proportions of the twoconstituents of what becameknown as Bordeaux mixture.Numerous field trials wererequired to establish the optimalformula. We now know thatmixing CuSO4 with limegenerates the active ingredientcupric hydroxide, which isstabilised by calcium sulphate.

Given Millardet's first-handexperiences of the Franco-Prussian war . . . and the ill-will

towards Germany still felt by many Frenchmen at the time, itis to Millardet's great credit that it was in a German journalin which in 1883 he first gave notice of his discovery,writes Ayres. His open-mindedness was rewarded, however,because when others claimed precedence for their own 1885publications, he could point to his article in the Zeitschrift furWein-Obst-und Gartenbaupublished two years earlier.

Bordeaux mixture was adopted rapidly, not only byvineyard owners throughout France but by potato growers inNorth America and elsewhere around the world. It had aconsiderable economic impact, safeguarding vulnerable crops,averting hunger, and thus saving lives. What a pity that todayMillardets statue, covered in verdigris, stands in a run-down

part of his adopted city, and is not even mentioned in the localguidebook. Perhaps he should have been more pushy.

Pushing Bordeaux mixture

Bernard Dixon

130 Cornwall Road, Ruislip Manor, Middlesex HA4 6AW, UK

594

The last word

Infectious Diseases Vol 4 September 2004 http://infection.thelancet.com