44 BULLETIN 866, IT. 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 iime 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- 
