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 lute 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- 



