PICKERING SPRAYS. 



9 



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 

 (PhytopTiihora 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 



Pickering (C) 



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 

 7 



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 



6 



957 







1,009 



5 





.23 

 1.25 

 .065 



963 





Bordeaux, 5-5-50 



1,027 



4 



915 



Check 





957 



3 





.13 

 1.25 



.36 



901 





Bordeaux, 5-5-50 



Pickering (C) 



1,260 



7 



1,260 



Check. .. 





1,335 



1 





.64 

 1.25 



.38 



1,426 





Bordeaux, 5-5-50 



1,386 



2 



1,208 



Check. . . 





1,190 



2a 



Pickering (A) androsin- 

 fish-oilsoap. 



.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 (PhytopJithora 

 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 



1 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 



