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



ering sprays did not materially influence their adhesive properties on 

 potato leaves. No injury to the leaves or to the potato plants was 

 caused by any of the Pickering sprays tested. 



The amount of copper sulphate essential for the control of late 

 blight on potatoes in Maine may be reduced 44 per cent by the use of 

 Pickering sprays. The amount of lime required is reduced also and 

 all grit removed from the spray, while at the same time the wear and 

 tear on spray machinery is greatly diminished. These results were 

 obtained in Maine where the principal potato trouble is late blight. 

 It is impossible to state what the efficacy of Pickering sprays on 

 potatoes would be in sections where other troubles predominate. 



BARIUM-WATER SPRAYS. 



Tests with a barium-water spray containing 0.7 per cent of copper 

 sulphate showed that it gave practically the same control of late blight 

 and the same yields as Bordeaux, 5-5-50. In fact, in 1917 and 1918 

 the yields were slightly larger on plats sprayed with barium wate? 

 than on those sprayed with Bordeaux. 



REDUCED-MILK-OF-LIME SPRATS. 



The 3-1^-50 spray tried in 1917 (a severe blight year) gave a 

 larger yield and a lower blight reading than the 3-3-50 spray. In 

 1918, the blight readings for the plats where the 4-1-50 spray was 

 employed were a little higher than for those where the 4-4-50 spray 

 was used. Apparently the amount of lime present in a Bordeaux 

 spray used for potatoes in Maine has little effect on the fungicidal 

 power. As long as sufficient lime is present to combine with the cop- 

 per, the extra lime has no fungicidal advantage, but has several dis- 

 advantages. 



Less copper adhered to the leaves when a 4-1-50 spray was em- 

 ployed than when 4-4-50 and 4-2-50 sprays were used. This may 

 be explained by the presence of free copper sulphate in the 4-1-50 

 sprays. 



STANDARD BORDEAUX SPRAYS. 



In sections where the blight may be severe, such as northern 

 Maine, a Bordeaux, 5-5-50, is recommended. In other States where 

 the blight is usually less severe a Bordeaux, 4-4-50, is desirable. 



GRAPES. 



Control of Fungous Diseases, 

 in new jersey. 



Four acres of Concord grapes near Vineland, N. J., were treated 

 with Pickering (A) and (C) sprays, varying in copper sulphate con- 

 tent from 0.065 to 0.64 per cent, and with a standard Bordeaux, 



