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



second set on July 24, four weeks after the last sprays had been 

 applied (Table 13). 



The most actual copper was found on the leaves sprayed with 

 Bordeaux containing 1 per cent of copper sulphate (plats 8, 9, and 

 10). Calculated per 0.1 per cent of copper sulphate present in the 

 sprays, the leaves from plats 4, 5, and 6, sprayed with the two Pick- 

 ering sprays and the barium-water spray, and gathered directly 

 alter the sprays had been applied, gave the highest results. Of the 

 leaves gathered four weeks after spraying, those treated with the Bor- 

 deaux sprays (plats 8, 9, and 10) and with the Pickering sprays 

 (plats 5 and 6) gave the highest proportional results. The barium- 

 water spray and the two sprays made with sal soda did not adhere to 

 the leaves for the four-week period as well as the sprays made with 

 lime. The percentage of rotten berries found on the two plats 

 sprayed with the sal-soda sprays was low, in spite of the relatively 

 small amounts of copper adhering to the leaves at the time of analysis. 

 Apparently, therefore, the amount of copper adhering to a leaf is not 

 necessarily a criterion of its protection from fungous diseases. 



Injury to Leaves and Fruit. 



No caustic action of any of the sprays was noted in either 1917 or 



1918. 



Summary. 



None of the sprays tested injured the leaves or berries. 



The Pickering (A) and (C) sprays were equally effective in control- 

 ling fungous diseases. Pickering (A) and (C) sprays prepared with 

 0.6 per cent of copper sulphate seemed to give as effective control 

 of fungous diseases on cranberries as Bordeaux, 4-3-50, containing 

 1 per cent of copper sulphate, although this was not definitely proven. 



Practically the same percentage of copper was present on the 

 cranberry leaves treated with Pickering spray as on those sprayed 

 with standard Bordeaux, rosin-fish-oil soap being used with all the 

 sprays. 



Additional tests with the. Pickering, barium-water, and sal-soda 

 sprays are necessary to obtain conclusive results. 



SUGGESTIONS FOR THE PREPARATION OF PICKERING SPRAY ON A 



COMMERCIAL SCALE. 



The following procedure is recommended for the preparation on 

 a commercial scale of a Pickering (A) spray containing 0.7 per cent 

 of copper sulphate : 



STOCK SOLUTION OF COPPER SULPHATE (BLUESTONE OR BLUE VITRIOL). 



Suspend 50 pounds of commercial crystalline copper sulphate 

 in a gunny sack in 20 or 30 gallons of water in a clean barrel over 



