12 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 
treated with Pickering sprays containing less than 0.4 per cent of 
copper sulphate yielded less than the corresponding Bordeaux- 
sprayed plats but more than the check plats. The yield of tubers 
from the sprayed plats showed an increase of from 30 to 40, per 
cent over that from the unsprayed plats. 
A high proportion of rotten tubers was found on all the plats. 
This was due principally to the wet weather, but partially to the 
late start made in applying the sprays. The percentage of rotten 
tubers from the various plats is too variable to permit of any definite 
conclusions. The tubers from the check plats showed no more rot 
than those from the sprayed plats. Barrels of potatoes from several 
of the plats treated with Pickering and Bordeaux sprays, as well as 
from the check plats, were stored in a potato cellar until February, 
1918, when the tubers were sorted. The percentage of rot found 
among the potatoes from the various plats was very uniform. 
In 1917 the blight was severe, and the land used for the experi- 
ments was uneven, which gave some of the plats a decided advantage 
over others. The results showed that a Pickering spray containing 
0.7 per cent of copper sulphate is in all respects as efficient as a 
Bordeaux, 5-5-50, containing 1.25 per cent of copper sulphate. 
No differences were noted in the relative efficiency of the Pickering 
(A) and (C) sprays. While these sprays were not shown to be 12 
times as effective as standard Bordeaux, the indications were that 
they were more efficient per unit of copper in the solution used than 
the Bordeaux mixture. 
PICKERING AND BORDEAUX SPRAYS IN 1918. 
Series 1. — Tests with Pickering (A) spray, containing 0.7 per cent 
of copper sulphate, were made on two farms in the vicinity of Presque 
Isle, as well as on the farm used in 1916 and 1917. Each spray was 
applied five times to acre plats, using a Watson sprayer, two nozzles per 
row, in two instances, and a new single-nozzle sprayer in the other. 
Twice during the season the vines were double sprayed. 
The blight, while widespread in July, and threatening to do as 
much damage as in the previous season, was stopped by the dry 
weather during August. The blight readings on the vines, made by 
three individuals working independently, were low, 2 per cent. or less, 
for the Pickering- and Bordeaux-sprayed plats. The check plats 
showed from 20 to 50 per cent of blight. Evidently, then, the 
Pickering sprays applied in 1918 checked the blight as effectively 
as did the Bordeaux mixture. 
The yield results on two of the farms varied greatly, according to the 
location of the plats, because of an uneven distribution of manure 
and fertilizer over the fields. On the farm previously used for the 
