11 Ai;(j., 1919.] Copper Fungicides. 48;^ 



COPPER FUNGICIDES. 



//y /'. Je Cdstella, (>'overnment V/tiruIfitrtft . 

 (Continued from page 112.) 

 Copper Acetates or " Verdets."* 



After Bordeaux Mixtures and Copper Soda the best known and most 

 widely-used Copper Fungicide is Acetate or more correctly, the Copper 

 Acetates, for there are really several of these salts. They may, however, 

 be considered under two headings — 



1. Basic Copper Acetates — V( rdet-gris or in English-, verdegris — 



of somewhat variable composition, as will be explained 

 later, but consisting mainly of bi-basic copper acetate — 

 Cu (C,H,0..)XiiH.,0^ 



2. Neutral Copper A'cetate— Cu(CJl303)2H,0. 



Both constitute excellent fungicides, presenting similar advantages to 

 '' Bordeaux " and Copper Soda, in the way of immediate activity, and an 

 adherent and durable reserve of copper; the deposit left on the tissues 

 of the vine is sufficiently insoluble to afford lasting protection and yet 

 soluble enough to constitute a powerful germicide. They present, in 

 addition, the important practical advantages of not scorching the foliage, 

 freedom from nozzle trouble and are very convenient as regards the 

 making up of the spray mixture since they only require mixing with 

 water, without addition of lime soda, &c., It is not too much to sav 

 that but for their rather higher cost the acetates would in all probability 

 liave superseded the other copper spray preparations. 



Copper acetate is by no means a new fungicide. Verdegris, tlie ba-ic 

 form, appears to have been first proposed by M. Georges Bencker, of 

 .Montpellier, in 1886. The manufacture of this salt, as a by-product of 

 wine making, constituted an important industry in the South of France 

 iiiany years ago. It is indeed curious that this same siibstance should 

 now prove so valuable a specific for the treatment of vine diseases. This 

 use, in fact, seems likely to bring about a revival of the almost extinct 

 verdegris industry which at one time supplied the needs of colour manu- 

 facturers, calico dyers, &c., in France and other countries. 



The neutral acetate is of more recent introduction. Opinions differ 

 somewhat as to the relative merits of the two, but both have been found 

 to possess fungicide properties of a high order. It is somewhat strange 

 that the eleventh report of the Woburn Experimental Fruit Farm 

 (1910) which deals exhaustively with copper fungicides, should devote 

 so little attention to copper acetates. Concerning the basic form, the 

 only one mentioned, in addition to recording its occasional use it is 

 merely stated that " the fungicidal properties of verdigris are not 

 spoken of very highl^^" On the other hand in all French text books 

 from Viala's les MdJadies de la Yigne onwards, verdegris, and more 

 recently, the neutral acetate, are considered to be equal if not superior 

 to the other copper sprays. 



Both acetates contain a higher percentage of metallic copper than 

 bluestone or crystallized copper sulphate (CuSO^ ..511^0) the copper 

 content of which is 25 per cent. The neutral acetat/e contains 31 per 

 cent., wliile verdegris contains from 33 to 35 per cent, of the metal. 



* Vcrdei is a generic term given collectively, in France, to the copper acetates. The word is often useJ 

 i n the plural " les renlets " to include rerdet-qrif: or \ ordegris and venlcl iifi'lre, the neutral or normal acetate. 



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