PICKERING SPRAYS. 



27 



IN VIRGINIA. 



On June 10 a heavy hail storm broke the leaves, punctured the 

 grapes, and broke off many shoots from the vines. Two or three days 

 after the storm serious burning of the leaves was noticed. This in- 

 jury was particularly severe on the plats sprayed with the strongest 

 Pickering solutions. The weakest Pickering spray produced about 

 the same injury as the Bordeaux spray. On June 26 new growth 

 appeared on all the sprayed vines, and a fourth spraying was made 

 on July 3, with no additional spray injury. As in the case of the 

 tests in New Jersey, the injury to the leaves was in direct proportion 

 to the percentage of copper sulphate present in the Pickering sprays. 



Among the numerous theories advanced to explain the burning 

 or scorching of. foliage by copper sprays are the following: (1) A 

 specific susceptibility of the protoplasm of the plant to copper; 

 (2) solvent properties or activities of the cell sap of the plant on the 

 copper compound of the spray; (3) permeability of the epidermis or 

 cuticle to the cell contents when conditions are favorable for exos- 

 mosis and for a trace of copper which has been rendered soluble; 

 (4) weather conditions following spraying, particularly moisture, 

 which provides suitable conditions for the exosmosis of some of the 

 contents of the cells of leaves; (5) the amount of spray on the leaves 

 or foliage, the proportions of other constituents, such as lime, to the 

 copper in the spray, the condition of the leaves, whether normal or 

 injured by the weather, insects, etc., and, above all, the climate. 



Effect on Maturing of Fruit. 



in virginia. 



At the time of picking, samples of grapes from the different plats 

 were analyzed for reducing sugar, sucrose, and acidity, using the 

 methods of the Association of Official Agricultural Chemists, in 

 order to determine the influence of the sprays in preventing a proper 

 maturing of the fruit. 





Table 



9. — Effect of various sprays on 



composition of 



grapes ( Virginia) 







Hat. No. 



Spray used. 



Copper 



sulphate 



in spray 



used. 



Composition of grapes at 

 picking time. 





Reducing 

 sugar. 



Sucrose. 



Acidity. 



A 



Bordeaux, 3-3-50 





Per cent. 

 0.75 

 .64 

 .38 

 .38 

 .13 

 .23 

 .36 



Per cent. 

 7.35 

 10.52 

 8.57 

 8.54 

 7.50 

 9.10 

 7.60 



Per cent. 



0.07 



.22 



.42 

 .10 

 .10 

 .28 

 .20 



Cc. nor- 

 mal al- 

 kali per 

 kilo. 

 162 



1 





152 



2 



do 



159 



2b 





Pickering (A) and rosin-fish-oil soap. 





157 



3.. 







155 



5 





152 



7 



do 



151 









