SPRAYS AND SPRAYING 131 



deaux is reported to be as efficient as newly mixed,' 

 but generally these preparations are much inferior to 

 the newly prepared, and, when applied dry, are less 

 effective than in the wet form. 



Washing Soda and Copper Sulphate Mixture. 

 — This mixture is being used with success in parts of 

 Europe. It does not clog nozzles, spreads evenly over 

 the leaf, and is easily and cheaply prepared. The 

 washing soda is dissolved in water, poured into the 

 barrel of water and stirred, and the copper sulphate 

 added and stirred. Various strengths are in use, but 

 the most satisfadlory one for American conditions has 

 yet to be determined. We are trying 4 pounds of cop- 

 per sulphate, 6 pounds of washing soda, and 50 gallons 

 of water, adding i pound of lime if Paris green is used. 

 A little over i pound of washing soda might be suffi- 

 cient to neutralize the 4 pounds of copper sulphate, but 

 it is safer to use more. In Ireland 5 pounds are used 

 and for three successive 3'ears in extended trials this 

 mixture has given better results than Bordeaux mix- 

 ture.' At (N. Y.) Geneva Station, in 1904, it was not 

 so good as ordinary Bordeaux mixture. 



Spraying with Bordeaux Mixture. — Benefits. — 

 Spraying with Bordeaux mixture influences the potato 

 crop in the following ways : 



1 . The strucflure ^ of the leaf shows a slight increase 



in thickness and in strength, and so offers more 

 resistance to the growth of disease spores. 



2. The chlorophyll,^ or green coloring matter of the 



leaf and stem, is increased. 



J Me. Bui. 73, p. 55. ' Department of Agric. for Ireland I<eafiet, 14. 



» Frank & Kruger. E. S. R., VI., p. 306. 



