44 BULLETIN 866, TJ. S. DEPARTMENT OF AGRICULTURE. 



limewater may be drawn off by suction through a hose into the 

 mixing tank or barrel. 



In making saturated limewater, 2 pounds of unslaked lime, or 4 

 pounds of lime paste, to 50 gallons of water are sufficient. 



MIXING. 



Add 23.1 quarts of the standard copper sulphate solution (1 pound 

 to a gallon) to a 100-gallon tank containing 93.78 gallons of clear 

 saturated limewater, and stir for 1 minute. Lead arsenate or cal- 

 cium arsenate may then be added if desired, and 0.42 gallon of water 

 to make the volume to 100 gallons. 



The method of preparing limewater is the principal distinction 

 between making the Pickering and the standard Bordeaux sprays. 



In the experience of the writer, the Pickering sprays are readily 

 prepared, in much less time than many of the proprietary pastes 

 which dissolve with difficulty, and take but little more time than 

 the standard Bordeaux sprays require. 



SUMMARY. 



Experiments- covering three seasons were conducted with Pickering 

 (A) and (C) .sprays, made to contain from 0.06 to 0.70 per cent of 

 copper sulphate. The efficacy of these sprays was compared with that 

 of standard Bordeaux mixtures containing from 0.75 to 1.25 per cent of 

 copper sulphate. The investigation was carried out under American 

 field conditions, in regions where certain fungous diseases are most 

 severe. 



The strongest Pickering sprays, those containing from 0.6 to 0.7 

 per cent of copper sulphate, controlled fungous diseases on potatoes 

 and cranberries very effectively. Their control of fungous diseases 

 on grapes and apples was not definitely determined, the results 

 being complicated by burning or other injury to the foliage and 

 fruit. Pickering sprays containing less than 0.6 per cent of copper 

 sulphate were not effective as fungicides for potatoes and probably 

 not for cranberries. No difference between the efficacy of the 

 Pickering (A) sprays and that of the Pickering (C) sprays was 

 observed. The results of the tests made on potatoes indicated that 

 per unit of copper present the Pickering sprays were twice as effec- 

 tive as the Bordeaux mixture. No evidence, however, was found to 

 substantiate the claims of Bedford and Pickering (3, 4) that they 

 were from 12 to 15 times as efficient as the standard Bordeaux 

 sprays. As long as enough lime to combine with the copper was 

 present, the reduction of the lime content of Bordeaux sprays did 

 not alter their fungicidal value. 



Increased yields of tubers were obtained on plats of potatoes 

 treated with Bordeaux and with the stronger Pickering sprays, in- 



