10 Oct.. 1918.] Copper Fungicides for Vine Diseases. 593 



From the first haphazard sprinklings to the methodical use of logic- 

 ally-prepared Bouillie bordelaise (literally Bordeaux pap) or Bordeaux 

 Mixture, was a simple evolution carried out by French vine-growers 

 under the guidance of Millardet and other scientists. It is indeed 

 strange that French viticulture should thus, at the very beginning of 

 the fight against Mildew, have had the good fortune to accidentally hit 

 upon the copper fungicide, which is still the most efficient and generally 

 useful, and which has not been displaced as first favorite after nearly 

 40 years of experimentation. 



Bordeaux Mixture fills all the requirements of a perfect fungicide. 

 An entirely soluble substance would be washed oif by the first heavy 

 shower ; its application would need constant renewal in a wet season. 

 The precipitate of Bordeaux Mixture, however, is practically insoluble, 

 though not entirely so. Part of it is slightly soluble, and under the 

 action of the carbonic acid of the air further portions are gradually 

 rendered more or less soluble, so that the " reserve of copper " which 

 adheres to the green organs of the vine after a spraying continuously 

 makes available quantities of soluble fungus poison, minute it is true, 

 but sufficient to prevent spore germination. It is held by most authori- 

 ties that two to three parts of copper sulphate in 10,000,000 parts of 

 water is sufficient to inhibit the germination of Mildew spores. 



The sediment of Bordeaux Mixture also possesses considerable power 

 of adherence; this is sufficient to resist, in a marked degree, its removal 

 by rain. Once it has been allowed to dry on the vine, it is only after 

 continuous and violent rains that the spray substance is washed oif; 

 storm showers are far more potent in this respect that ligfht, misty rain. 



The nature of the precipitate, its solubility, and its power of adher- 

 ence vary considerably according to the method of preparation, and in a 

 certain measure to the presence of some substances wdiicli may be added. 

 It follows that several modifications have from time to time been made 

 in the mode of preparation, and there are at the present time numerous 

 distinct recipes in practical use. 



The formula first recommended by Professor Millardet in 1885 was 

 very strong; it contained 8 per cent, of copper sulphate and 15 per cent, 

 quicklime (40 lbs. copper sulphate and 75 lbs. quicklime to 50 gallons 

 of water). It was soon found that a much weaker mixture afforded 

 almost equal protection. The proportion of copper sulphate was first 

 reduced to 3 per cent., and later to 2 and even to 1 per cent., the quan- 

 tity of lime being even more considerably reduced, only sufficient of this 

 last substance being employed to neutralize the acidity of the copper 

 sulphate as shown by test papers. 



What may be termed Standard Bordeaux Mixture, which has for 

 some years past been recommended in the majority of French, viticul- 

 tural hand-books, consists of 2 per cent, copper sulphate crystals and 1 

 per cent, quicklime of good quality. In other words, 2 lbs. of copper 

 sulphate and 1 lb. quicklime to every 10 gallons of water. The copper 

 sulphate is dissolved in about 8 gallons of water ; the lime is slacked and 

 made into a milk in one gallon of water. The latter is poured into the 

 former — on no account should this order be reversed — with constant 

 stirring, and the bulk make up to 10 gallons by the addition of a little 

 water. Since lime varies greatly in purity, it is generally recom- 

 mended to be guided by test paper rather than by the weight of lime 



