PICKERING SPRAYS. 
used on plats 5, 6, and 7) were made by Formula C. All the Pickering 
sprays were applied with a hand-pump apparatus on July 19 and 
August 2, 10, and 17. Bordeaux was applied on these days, and 
also on July 26. Thus the Pickering sprays were applied four and the 
Bordeaux five times. Readings for blight, both early and late, were 
made by three observers working independently, those for the late blight 
(PliytopJithora infestans) being made on the two middle rows of each 
plat. The average figures obtained from two observations by each of 
these individuals are recorded, in terms of the estimated percentage 
of the total foliage infected, in Table 1. The potatoes from the 
several plats were picked up separately and weighed, the yield results 
thus obtained being given in Table 1 . 
Table 1. — Effect of various sprays on blight and yield of potatoes (northern Maine, 1916). 
Spray used. 
Copper 
sulphate 
in spray 
used. 
Early blight. Late blight. 
Yield of tubers. 1 
Plat No. 
Front of 
field. 
Rear of 
field. 
Front of 
field. 
Rear of 
field. 
Front of 
field. 
Rear of 
field. 
Bordeaux, 5-5-50 
Percent. 
1.25 
.115 
Per cent. 
52 
67 
66 
64 
59 
63 
68 
65 
50 
61 
67 
64 
56 
63 
59 
72 
Per cent. 
59 
73 
80 
78 
78 
86 
83 
78 
41 
58 
68 
55 
58 
61 
64 
70 
Per cent. 
,7 
40 
60 
43 
5 
53 
53 
13 
7 
36 
54 
27 
4 
21 
21 
5 
Per cent. 
4 
5 
7 
5 
2 
6 
7 
5 
2 
6 
21 
4 
3 
12 
3 
Pounds. 
1,189 
1,165 
1,202 
1,221 
1,225 
1,170 
1,189 
1,187 
1,252 
1,283 
1,309 
1,260 
1,276 
1,313 
1,220 
1,179 
Pounds. 
1,026 
957 
6 . 
Check 
1,009 
5 
.23 
1.25 
.065 
963 
Bordeaux, 5-5-50 
Pickering (A) 
1,027 
4 
915 
Check. . 
957 
3 
Pickering (A) 
.13 
1.25 
.36 
901 
Bordeaux, 5-5-50 
Pickering (C) 
1,260 
7 
1,260 
Check. . 
1,335 
1 
Pickering (A) 
.64 
1.25 
.38 
1,426 
Bordeaux, 5-5-50 
1,386 
2 
1,208 
Check. 
1,190 
2a 
Pickering (A ) and rosin- 
fish-oil soap. 
.38 
1,016 
1 Determinations were made on 200-foot depth of field, four -row plats. 
The blight in 1916 was not severe. The late blight on the potatoes 
under observation was very irregular, being marked in certain parts 
of the front of the field, particularly on the check plats, while the rear 
showed but little. On August 24 the vines in plat 1 and in those 
sprayed with Bordeaux were green, while those in all the other plats 
had died. 1 The best results for the control of late blight (PJiytoplitJiora 
infestans) on potatoes were obtained with standard Bordeaux, 5-5-50. 
The average estimated percentage of late blight on all of the plats 
sprayed with Bordeaux was 4^, the extremes being 2 and 7. 
The average yield for all of the plats sprayed with standard Bor- 
deaux was 1,205 pounds of tubers, and for the check plats 1,176 
pounds. Plat 1, sprayed with the Pickering (A) spray, containing 
0.64 per cent of copper sulphate, averaged 1,343 pounds of tubers, 
and showed 27 and 4 per cent of blight in the front and rear portions 
i A portion of this field was sprayed commercially by the owner, starting with a Bordeaux, 4-4-50, and 
finishing with a Bordeaux, 7-7-50 or 8-8-50. Neither the length of life of the vines nor the yield was in- 
creased by this treatment. 
180971°— 20— Bull. 866 2 
