PICKERING SPRAYS. 21 
still lower ones. The solution of copper sulphate and lead arsenate 
did not seem to adhere to the leaves as well as the other sprays. 
SUMMARY. 
The various Pickering and Bordeaux sprays tested adhered equally 
well to the potato leaves. Little difference was noted between the 
adhesive property of the copper from the Pickering (A) and that of 
the copper from the Pickering (C) solutions. The 1916 results favored 
the Pickering (C) spray, while the 1917 results were higher in the case 
of Pickering (A) sprays. The addition of either rosin-fish-oil soap or 
lead arsenate to a Pickering spray failed to increase its adhesive 
properties. In 1916 the results on leaves sprayed with barium-water 
spray were higher than, in 1917 lower than, and in 1918 equal to 
the standard Bordeaux results. A reduction in the amount of milk 
of lime used in preparing a standard Bordeaux type of spray did not 
appear to influence the adhesive properties of the spray until the 
amount used was less than that necessary to combine with the copper 
present, when a decrease in adhesive power resulted. The copper of 
the Burgundy mixture (sal-soda Bordeaux) did not adhere as well as 
the copper of standard Bordeaux, for the reason that all of the copper 
had not been precipitated by the sal soda. 
Injury to Vines and Tubers. 
No injury to vines or tubers was observed as the result of the appli- 
cation of any of the sprays used in these tests. 
Summary, 
pickering sprays. 
A Pickering spray containing 0.7 per cent of copper sulphate con- 
trolled the late blight as well as, and gave yield results equal to those 
obtained with, Bordeaux, 5-5-50, containing 1.25 per cent of copper 
sulphate. The copper in the Pickering sprays was apparently twice 
as effective as that in standard Bordeaux, 5-5-50. Pickering sprays 
containing 0.6 per cent of copper sulphate gave the same yield of 
tubers and nearly as effective control of late blight as Bordeaux, 
5-5-50. Pickering sprays containing less than 0.6 per cent of copper 
sulphate did not give satisfactory control of late blight. The claims 
of Bedford and Pickering (3, 4) that the copper of the limewater 
sprays is from 10 to 12 times as effective as the copper of standard 
Bordeaux were not substantiated by the results of these experi- 
ments. Pickering (A) and (C) sprays were found to be equally 
effective in controlling late blight on potatoes. 
The Pickering sprays adhered to the leaves as well as standard 
Bordeaux. The use of rosin-fish-oil soap or lead arsenate with Pick- 
