PICKERING SPRAYS. 
11 
per sulphate. Green Mountain (Norcross strain) potatoes, grown on 
new land, were sprayed six times during the season, using a Watson 
sprayer, after the vines were 10 or 12 inches above the ground. 
Portions of the two middle rows of each plat were read for blight 
and used for the yield data. The blight readings (Table 2) are the 
averages of the last readings of four individuals who worked inde- 
pendently of one another. The results obtained with Bordeaux spray 
(PL I, fig. 1) are more favorable than those secured from using 
the Pickering spray, with the exception of that applied to plat 1, 
where they were equally as good (PI. I, fig. 2). The Pickering 
sprays which contained less than 0.5 per cent of copper sulphate did 
not control the blight as effectively as the standard Bordeaux and 
the Pickering sprays containing 0.6 or 0.7 per cent of copper sulphate. 
Table 2. — Effect of various sprays on blight and yield of potatoes (northern Maine, 1917). 1 
i 7. 
Plat No. 
Check. 
Check. 
Check. 
Check. 
Check. 
Check. 
Check. 
Check. 
Check. 
Check. 
Check. 
Pickering (A) 
Bordeaux, 5-5-50. 
Copper 
sulphate 
in spray 
used. 
Per cent. 
0.7 
1.25 
Pickering (A) 
Bordeaux, 5-5-50. 
0.6 
1.25 
Pickering (C) 
Bordeaux, 5-5-50. 
Pickering (A) 
Bordeaux, 5-5-50. 
Pickering (C) 
Bordeaux, 5-5-50. 
Pickering (A) . .. . 
Bordeaux, 5-5-50. 
Pickering (C) 
Bordeaux, 5-5-50. 
Pickering (C) 
Bordeaux, 5-5-50. 
Pickering (A) and rosin-fish-oil ! 
Bordeaux, 5-5-50 
Pickering (A) and lead arsenate. 
Bordeaux, 5-5-50 
Pickering (C) and lead arsenate. 
Bordeaux, 5-5-50 
0.6 
1.25 
0.5 
1.25 
0.5 
1.25 
0.4 
1.25 
0.4 
1.25 
0.3 
1.25 
0.5 
1.25 
0.5 
1.25 
0.5 
1.25 
Late 
Yield of 
blight. 
tubers. 
Per cent. 
Pounds. 
44 
406 
45 
384 
57 
347 
52 
409 
41 
414 
85 
321 
48 
404 
42 
415 
95 
335 
53 
392 
42 
393 
88 
301 
53 
349 
43 
325 
84 
296 
67 
355 
37 
415 
96 
309 
76 
. 381 
39 
399 
96 
320 
63 
337 
41 
451 
96 
270 
56 
345 
41 
366 
96 
294 
56 
406 
42 
430 
96 
270 
57 
358 
44 
396 
96 
294 
Rotten 
tubers. 
Per cent. 
12 
14 
12 
13 
10 
10 
10 
11 
10 
12 
10 
10 
14 
8 
12 
10 
11 
7 
. 11 
i Determinations were made on two rows, each 300 feet long. 
The total yield results for plats 1, 2, and 3, treated with Pickering 
sprays, and for the corresponding Bordeaux-sprayed and check plats 
are as follows: Pickering, 1,219 pounds; Bordeaux, 1,213 pounds; 
and check, 1,003 pounds. Plats 4 and 5, to which the Pickering 
spray having an 0.5 per cent copper sulphate content was applied, 
yielded 741 pounds of tubers; the corresponding Bordeaux-sprayed 
plats, 718 pounds; and the check plats, 597 pounds. The plats 
