PICKERING SPRAYS. 
13 
experimental work, however, where the treatment of the soil was 
uniform, increased yields were obtained from the plats treated with 
the Pickering and Bordeaux sprays. 
Series 2. — A second series of tests was conducted in northern 
Maine in 1918, using (1) a Bordeaux spray, (2) Pickering (A) and (C) 
sprays, (3) a spray in which the limewater was replaced by barium 
water, and (4) an 0.6 per cent solution of copper sulphate to which 
powdered arsenate of lead (1 pound to 50 gallons) had been added. 
In all cases the sprays were made to contain 0.6 per cent of copper 
sulphate. Green Mountain (Norcross strain) potatoes were first 
sprayed when the vines were 5 or 6 inches above the ground, after 
which they received five applications with a Watson sprayer, using 
two nozzles to a row. The results of this work are recorded in Table 3. 
Table 3. — Effect of various sprays on blight and yield of tubers (northern Maine, 1918). 
Plat No. 
Spray used. 
Copper 
sulphate 
in spray 
used. 
Late 
blight. 
Yield of 
tubers. 1 
Per cent. 
0.7 
.7 
1.25 
1.0 
- 1.0 
1.0 
Per cent. 
2.0 
1.0 
1.7 
1.0 
3.0 
2.7 
20-50 
1.2 
1.6 
1.2 
1.5 
1.7 
1.8 
1.3 
2.3 
2.0 
1.-3 
1.9 
2.5 
.5 
33.0 
1.7 
1.3 
3.0 
1.7 
1.8 
1.2 
45.0 
Pounds. 
274 
Barium water 
277 
247 
Bordeaux, 4-4-50 
276 
Bordeaux, 4-2-50 
258 
Bordeaux, 4-1-50 '.... 
277 
Check 
215 
Farm 2 
.7 
.7 
1.25 
1.0 
1.0 
1.0 
.7 
.7 
1.25 
1.0 
1.0 
1.0 
1.25 
261 
264 
Bordeaux, 5-5-50 
279 
243 
Bordeaux, 4-2-50 
198 
222 
Farm 3 
227 
Barium water 
303 
224 
Bordeaux, 4-4-50 
295 
Bordeaux, 4-2-50 
370 
Bordeaux, 4-1-50.. . 
375 
Farm 1 (2d series): 
1 
244 
2 (check) 
235 
3 
.60 
.60 
.60 
.60 
.60 
1.25 
241 
4 
Pickering (C) 
251 
5 
Bordeaux, 2i-2i-50 
248 
6... 
241 
7 
237 
8 
242 
9 (check) 2 
175 
Determinations made on two rows, each 150 feet long. 
Plat partially shaded. 
The blight readings of all the plats sprayed were practically the 
same (1 to 3 per cent), while the vines on the check plats showed 
33 and 45 per cent infection. The yields were remarkably uniform 
for all the plats, with the exception of the last check plat, which was 
shaded by the adjacent trees. The dry season and the fact that the 
vines were killed by frost on September 9 tended to reduce the 
increased yields which are usually obtained from sprayed plats. 
Here the Pickering sprays containing 0.6 per cent of copper sulphate 
