70 PROTECTIO"N OF PLAISTS, 1920-21 



The above tables show neither system to have the advantage when all the 

 years were considered, but when only the heavy infestations are considered there 

 is a slight difference amounting to .8 per cent in favor of spraying. At Hem- 

 mingford the following results were obtained in years of heavy infestation : 



Year Unsprayed Sprayed Dusted 



1917 - 80..0 1..0 3..8 



1918 95.0 .4 ..4 



1919 93..0 20..5 62..3 



The above figures show both systems were satisfactory in 1917 and 1918 

 but decidedl}^ otherwise for dusting in 1919. There were 3 days separating 

 the 3rd application in 1919. The spraying was done on the 17th and the dust- 

 ing on the afternoon of the 20th. The weather was as follows : 



17th — Misty and warm. 

 18th — Clear and very warm. 

 19th — Very warm, rain at night. 

 20th — Cloud}", warm and muggj'. 



It is very probable that the scab developed very rapidly during these few 

 days and was largely responsible for the heavy infestation of the dusted apples. 



The sprays used were chiefly lime sulphur and arsenate of lead and dusts 

 arsenate of lead and dust sulphur. However, in Nova Scotia, Bordeaux mixture 

 was used sometimes and in Quebec arsenate of lime was used on several occ- 

 asions both in sprays and dusts. 



Another very important thing to consider is the injury to foliage and fruit 

 due to burning. This has appeared more or less severely for the past four years 

 in the sprayed areas but as j'et there has been no burning from the application 

 of dusts, which have contained as high as 15 per cent arsenate of lead or 10 per 

 cent arsenate of calcium. 



So far as biting insects are concerned all the results the writer has seen 

 show dusted arsenicals as good, and, in most cases, better than sprayed arsenic- 

 als. In this connection the following figures on wormy apples are taken from 

 Sanders' & Kelsalls' tables : 



Place 



New York. 



Michigan. 



Illinois 



Nova Scotia 



The above figures are all in favor of dusting. The codling worm upon 

 which apparently the above figures are based is only of minor importance in 



