484 Journal of Agriculture, Victoria. [11 Aug., 1919. 



Copper being the active fiDigicide agent, it follows that the acetates can 

 afford equal protection in weaker spray mixtures than are needed if 

 copper sulphate be employed. It is, indeed, generally admitted in 

 France that a 1 per cent, verdet spray (1 lb. of verdigris or of 

 neutral acetate to 10 gallons of water) is as effective as a 2 per cent. 

 Bordeaux or copper soda (2 lbs. bluestone to 10 gallons water with 

 the necessary lime or soda to neutralize). 



As regards cost — Since the two acetates differ so little in copper 

 content it may be assumed in practice that equal quantities of either 

 are needed to make up the spray mixture — viz., 1 lb. to 10 gallons of 

 water. In other words a 1 per cent, mixture as against 2 per cent, in the 

 case of copper sulphate. The pre-war price of copper sulphate in France 

 was £20 to £24 per ton as against £68 to £80 for verdigris; with the 

 latter, however, allowance must be made for the fact that no lime or soda 

 is required. 



According to Bencker,"' in pre-war times, the cost of the hectolitre 

 (22 gallons) of 2 per cent. Bordeau or Copper Soda, including cost of 

 lime or soda, was lOd. to Is., as against Is. 4d. to Is. 7d. for a similar 

 quantity of a 1 per cent, acetate mixture. 



N'otwithstanding this higher price many French vinegrowers treat 

 their vines with verdet in preference to other copper sprays, considering 

 that it affords equal if not more effectual protection and that the other 

 advantages more than compensate for the extra cost. 



Towards the close of the war the popularity of verdegris was 

 strikiaigly illustrated. Wholesale requisitioning of French acetic acid for 

 use in munitioii factories seriously hampered the manufacture of verde- 

 gris, the scarcity of which was so severely felt by vinegrowers that the 

 Confederation generale des vignerons, at a meeting held at Montpellier 

 on 6th August 1918, decided to petition the French Munitions Depart- 

 ment to remove or modify the embargo on acetic acid. This was granted 

 just before the armistice, the French Government consenting to supply 

 verdet manufactures in order that this favourite fungicide might be 

 made available to vinegrowers. 



The importance of increasing the spreading or wetting power of 

 spray mixtures by the addition of casein, soap and other substances has 

 already been pointed out. Casein can onlv he used with an alkaline 

 mixture; being curdled by acids it is unsuitable in the case of copper 

 acetates, the reaction of which is slightly acid; it can, however, be 

 replaced by gelatine at the rate of 1 oz. to 10 gallons of copper acetate 

 spray mixture. 



Kn important advantage of the acetates — both basic and neutral — is 

 that they do not deteriorate after mixing. Bordeaux mixture, and more 

 particularly copper soda, are of little value unless freshly prepared; with 

 the acetates, on the other hand, no change takes place. Large vats of 

 stock solution (or mixture) can therefore be made up, to he diluted to 

 the 1 per cent, strength as may .be required. 



Verdegris, and more particularly the neutral acetate, leave less 

 visible traces on the foliage than do Bordeaux or copper soda. This 

 defect, though without importance as regards protection against fungus 

 disease, complicates the supervision of the work; it is easily obviated by 

 the addition of a small proportion of some light inert powder such as 



♦ nerme de Viticulture, 7th November, 1918. 



