28 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 



The results (Table 9) naturally varied with the condition of the 

 individual samples. The grapes from plat A, sprayed with standard 

 Bordeaux mixture, showed the highest acidity and the lowest sugar 

 content, while those from plat 1, treated with Pickering spray con- 

 taining 0.64 per cent of copper sulphate, gave the highest content 

 of sugar and a low acidity. Since the percentage of sugar increases 

 and the percentage of acidity decreases during the ripening of grapes, 

 no influence of the sprays in preventing- a proper maturing of the 

 fruit is indicated. On the contrary, an increase in the sugar con- 

 tent and a decrease of acid is evident in the Pickering-sprayed grapes, 

 compared with those sprayed with Bordeaux. As no unsprayed 

 grapes were analyzed, it is impossible to state whether or not the 

 copper in the sprays exerted a stimulating action on the grapes. 



The variation in the composition of the grapes sprayed with Pick- 

 ering and Bordeaux may possibly be due to the greater availability 

 of the copper in the Pickering sprays. The fact that more burning 

 resulted from using the Pickering sprays than from using the 

 Bordeaux sprays is evidence of a greater availability, or at least 

 solubility, of the copper of the Pickering sprays. It has been sug- 

 gested that the effect of the sprays on the composition of the fruit 

 came through foliage injury. 



Summary. 



Pickering (A) and (C) sprays, containing 0.64, 0.36, and 0.38 per 

 cent of copper sulphate, caused severe injury to the grape foliage 

 and fruit after a hail storm which tore the leaves and injured the 

 vines both at Vineland, N. J., and Vienna, Va., in 1916. Under simi- 

 lar conditions the Pickering sprays containing 0.23, 0.13, 0.115, and 

 0.065 per cent of copper sulphate caused less injury than the stronger 

 Pickering sprays, but more injury than standard Bordeaux, 3-3-50, 

 containing 0.75 per cent of copper sulphate. 



The strongest Pickering spray, that employed on plat 1, controlled 

 the black rot fully as well as the Bordeaux, 3-3-50, and the Picker- 

 ing sprays containing 0.36 and 0.38 per cent of copper sulphate 

 showed practically as effective control as the Bordeaux. The weaker 

 Pickering sprays, containing 0.23 per cent of copper sulphate or less, 

 did not control the black rot as well as the Bordeaux spray. 



The yield of grapes was reduced by all of the Pickering sprays 

 except the two weaker ones. 



The copper of the Pickering sprays did not adhere to the grape 

 leaves as well as the copper of the Bordeaux, 3-3-50. The averages 

 of all the results obtained, including some not reported in the tables, 

 show that where the Pickering sprays were applied with a power 



