16 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 
case of those sprayed with standard Bordeaux and of from 20 to 50 
per cent in the case of the unsprayed plats. The barium- water- 
sprayed plats yielded from 264 to 303 pounds of tubers, the Bor- 
deaux-sprayed plats from 247 to 313 pounds, and the check plats 
215 pounds. 
The application of the 0.6 per cent barium-sulphate spray to 
smaller plats gave an average blight reading of 1.7 per cent, as com- 
pared with 0.5 and 1.2 per cent for the Bordeaux, 5-5-50, mixture, 
and 33 and 45 per cent when no spray was used. The yields of 
tubers from two rows, each 150 feet long, were: Bordeaux-sprayed 
plat, 244 pounds; check plat, 235 pounds; barium-water-sprayed plat, 
241 pounds. 
These results, extending over three seasons, particularly those of 
1917 and 1918, indicate that a spray made with barium hydrate and 
containing 0.7 per cent of copper sulphate gives a satisfactory control 
of blight and the same yield of tubers as a Bordeaux, 5-5-50, con- 
taining 1.25 per cent of copper sulphate. Plate II, figure 2, shows 
the protective action given by the barium-water spray in 1918, when 
the blight was severe. 
In preparing the barium- water spray containing 0.7 per cent of 
copper sulphate, equal parts of copper sulphate and barium hydrate 
(2.8 pounds of barium hydrate and 2.8 pounds of copper sulphate to 
50 gallons) were found to be satisfactory. While such a spray gave 
good results and reduced the copper sulphate used 44 per cent, the 
price of barium hydrate is so high that such a spray can not be con- 
sidered commercially practicable at the present time. If the price 
of barium hydrate drops, or if barium chlorid, which sells for $75 per 
ton, can be used, an effective spray may be cheaply prepared. The 
fact that no residue is left, that the barium hydrate may be added to 
the spray tank with the water and dissolved there, and that there is 
reduced wear and tear on apparatus, may induce a trial of this spray, 
particularly if the yields are shown to be stimulated to a greater 
extent than with Bordeaux, 5-5-50. 
REDUCED MILK-OF-LIME SPRAYS IN 1917. 
Bordeaux, 3-3-50 and 3-1J-50, sprays were applied to potatoes 
during the season of 1917. The reason for reducing the proportion 
of lime used as milk of lime was to determine its influence on the 
fungicidal power of the copper and its effect upon the adhesive prop- 
erties of the spray. 
Blight control. — Check plat, 71 per cent; plat sprayed with Bor- 
deaux, 5-5-50, 13 per cent; plat sprayed with Bordeaux, 3-3-50, 38 
per cent; and plat sprayed with Bordeaux, 3-1J-50, 26 per cent. 
Yield. — Check plat, 139 pounds; plat sprayed with Bordeaux, 
5-5-50, 158 pounds; plat sprayed with Bordeaux, 3-3-50, 148 
pounds; plat sprayed with Bordeaux, 3-1^-50, 172 pounds. 
