10 Dec, 1918.] Copper Fungicides for Vine Diseases. 735 



COPPER FUNGICIDES FOR VINE DISEASES. 



By F. de Castella, Government ViticidturiH. 



(Continued from page 678.) 



Substances which may be added to Bordeaux. 



In addition to acid, neutral and alkaline (or basic), Bordeaux 

 mixtures, a considerable number of formulae have from time to time 

 been suggested, and more or less widely used, in which the innovation 

 consisted in the introduction of some substance capable of modifying 

 the chemical or physical nature of the mixture. The addition of casein 

 has already been fully described (see pp. 598 and 675). As this appears 

 to be the most useful of all suggested additions, it was dealt with thus 

 early, so as to secure insertion in the October issue, thus making the 

 information concerning it available for the spraying season then about 

 to start. 



Though it would be out of place to consider in detail all the other 

 additions which have been suggested, a few of the more important ones 

 may be briefly considered; some of them may possibly be recommended 

 as novelties here, and a brief indication of the advantages and defects 

 of each may prove useful. 



Sugar or Treacle. — The addition of sugar to Bordeaux mixture 

 was strongly recommended by Michel Ferret in 1896. Of the many 

 " improvers " which have been suggested, it is still one of those most 

 worthy of attention ; curiously enough, however, " sugar Bordeaux " 

 seems to have largely gone out of fashion, so that it is now not extensively 

 used. In his original communication,* Ferret pointed out how, in order 

 to combat fungus diseases more efficiently, the copper should be rendered 

 soluble, so that its protective action might be insured from the very 

 start of growth. With this object in view, he tried the solubilization 

 of copper by sugar, so as to form a soluble copper saccharate (sucrate) 

 quite harmless to vegetation. This substance, owing to its adhesiveness, 

 resists the action of rain, thus dispensing with the repeated sprayings 

 necessary with most other mixtures. He suggested the mixing of lime 

 saccharate (sucrate) and copper sulphate. On thoroughly stirring this 

 powder into water, it entirely dissolves, yielding, by a double exchange of 

 bases, a spray mixture composed of lime sulphate, precipitated copper 

 oxide, and copper saccharate, the solution of which is of a fine green 

 colour. Of the copper saccharate thus obtained, one-half is in solutioii ; 

 this acts strongly on fungi, whilst it offers no danger to the vine. The 

 mixture can, therefore, be used with impunity from the very start of 

 growth. Three kilos per hectolitre (15 lbs. to 50 gallons) is the strength 

 he recommends. 



A composite sugar Bordeaux was subsequently advocated. This can 

 be obtained by the addition of treacle to ordinary or standard Bordeaux 

 mixture (containing 2 per cent, of copper sulphate crystals), at the rate 

 of 1 gallon of treacle to 50 gallons of spray mixture. The treacle should 

 be diluted and well mixed with about five times its bulk of water, and 

 stirred into the Bordeaux before its final dilution to the 50-galIon 

 bulk (see p. 559). In this composite mixture the treacle simultaneously 



* Revue de Viticulture, 22nd February, 1896. 



