PICKERING SPRAYS. 15 



Pickering sprays. While barium hydrate costs much more than 

 lime, barium, unlike lime, is dissolved, leaving no residue. Barium is 

 said to possess some fungicidal powers which lime does not. Oster- 

 hout (16) noticed a peculiar contraction of certain species of spyro- 

 gyra in 0.0001 molecular solution of barium chlorid, which was not 

 produced by chlorid of lime or other salts. 



A spray containing 0.38 per cent of copper sulphate was prepared 

 by dissolving barium hydrate in water and adding the copper sul- 

 phate solution to the barium water. When necessary more barium 

 water was added until no free copper was present, as determined by 

 tests with potassium ferrocyanide. 



In 1916 this spray was applied four times, while the regular 5-5-50 

 Bordeaux was applied _five times. The plats sprayed with barium 

 water were next to the check plats and the Bordeaux-sprayed plats 

 were between two sprayed plats. The blight readings were : Barium- 

 water-sprayed plats, 25 and 12 per cent; Bordeaux-sprayed plats, 

 12 and 10 p*er cent; check plats, 75 and 41 per cent. The yields of 

 tubers were: Barium-water-sprayed plats, 1,142 and 1,052 pounds; 

 Bordeaux-sprayed plats, 1,125 and 1,168 pounds; check plats, 1,058 

 and 1,138 pounds. In view of the fact that only 0.38 per cent of 

 copper sulphate was present in the spray and but four applications 

 were made, while the Bordeaux was applied five times, these results 

 were sufficiently satisfactory to warrant additional tests. 



BARIUM-WATER SPRAYS IN 1917. 



In 1917 a barium-water spray made to contain 0.7 per cent of 

 copper sulphate was tested. The average percentage of late blight 

 on the vines was: Check plat, 76 per cent; barium-water-sprayed 

 plat, 21 per cent; Bordeaux-sprayed plat, 13 per cent. The yield 

 of tubers and percentage of rot from the two middle rows of each plat, 

 each row being 100 feet long, were: Standard Bordeaux-sprayed 

 plat, 148 pounds, 8 per cent rot; barium-water-sprayed plat, 168 

 pounds, 5 per cent rot; check plat, 130 pounds, 6 per cent rot. The 

 barium-water-sprayed plat adjoined a check plat, while the Bor- 

 deaux-sprayed plat had sprayed plats on either side.. 



BARIUM-WATER SPRAYS IN 1918. 



In 1918 a barium-water spray containing 0.7 per cent of copper 

 sulphate, which had given excellent results in 1917, was tested on 

 acre plats in a •commercial way, and another barium-water spray, 

 containing 0.6 per cent of copper sulphate, was tested on a smaller 

 scale. 



The plats to which 0.7 per cent barium-water spray was applied 

 on the commercial scale gave blight yield readings of from 1 to 2.3 

 per cent as compared with readings of from 1.2 to 2.0 per cent in the 



