24 



BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 



deaux, 3-3-50, spray. The Pickering spray was used alone and in 

 combination with rosin-fish-oil soap. The sprays were applied four 

 times, May 15-16, May 25-26, June 12-13, and July 1-3, 1916, with 

 a barrel pump sprayer. 



Early in July many spots of black rot were seen on the leaves of 

 the check plat, but none on the leaves of the sprayed plats. On 

 June 26 some black-rot spots were observed on the leaves from all 

 plats except those sprayed with Bordeaux, 3-3-50, and Pickering 

 (A) containing 0.64 per cent of copper sulphate (plats A and 1). 

 Plat 7, sprayed with Pickering (C) containing 0.36 per cent of copper 

 sulphate, showed very few spots. The check plat showed the largest 

 number of infected leaves. One row of vines in plat 1 did not re- 

 ceive the second application. These vines showed neither the spray 

 injury nor the control of rot apparent in the rest of the vines of 

 plat 1. 



Table 7.- — -Effect of various sprays on black rot of grape leaves ( Virginia). 



Plat No. 



Spray used. 



Copper 

 sulphate 

 in spray. 



Amount 

 of black- 

 rot leaf 

 spot. 



Remarks. 



A 



Bordeaux, 3-3-50 



Per cent. 



0.75 



.64 



.38 



.38 



.13 

 .23 

 .36 



.00 



Per cent. 

 3.5 

 3.5 

 5.0 

 5.0 



11.0 



6.5 



5.0 



100.0 





1. 





2.... 



do 





2b 



Pickering ( A ) and rosin - 

 fish-oil soap. 



Do. 



3 



Slight burning of leaves. 

 Do. 



5. . 





7. 



do 



Leaves severely injured; fruit somewhat. 

 Vines not much injured. 



Check 









The results in Table 7 show that the four strongest Pickering sprays 

 tested (plats 1, 2, 2b, and 7) and the standard Bordeaux spray gave 

 an excellent control of black-rot leaf spot on the leaves. The sprays 

 used on plats 3 and 5 gave a less effective control of the disease. 

 Black-rot spots were seen on the leaves of all the vines on the check 

 plat. The weeds in the vineyard were high, and the weather was 

 moist, rendering conditions for infection excellent. Of all the ex- 

 perimental plats, No. 5 looked the best, although not as well as the 

 plat sprayed with standard Bordeaux. 



Yield. 



IN NEW JERSEY. 



The yield of grapes sprayed varied with the injury to the vines, 

 which in turn depended upon the percentage of copper sulphate in 

 the Pickering sprays employed. The two weakest (those used on 

 plats 4 and 6) gave good yield results, but plat 4 showed only 69 

 and plat 6 only 85 per cent of sound berries, as compared with 93 

 per cent obtained from the plat sprayed with Bordeaux, 3-3-50. 



