REPORT OF THE SOCIETY ()9 



infrequent where sprayers are used. Furthermore, to replace broken sprayer 

 parts is a difficult and tedious job, owing to the awkward position in which many 

 of the parts are located. With dusters most of the parts are easily accessible. 

 It is also true that the duster ready for action weighs less than a sprayer, but 

 this is not important in the majority of Quebec orchards. 



The two outstanding advantages in favor of dusting are : (1) When fung- 

 ous diseases develop most rapidly the weather is most suitable for dusting 

 but not for spraying ; and, (2) the greater speed, which allows rapid treatment 

 of large areas. 



Aside from the above differences, it must be remembered that both systems 

 must primarily be satisfactory for the control of fungous diseases, biting and 

 sucking insects. Of the fungous diseases black rot canker and apple scab are our 

 two most important apple diseases. As to the former, there is no evidence, to 

 the writer's knowledge, to prove t)iat dusting is or is not satisfactory for its con- 

 trol, but for the latter there is plenty of data to compare the two systems fairly 

 satisfactorily. 



The following figures are taken from Sanders' & Kelsall's article in Scien- 

 tific Agriculture, Vol. 1, No. 1, pp. 14-18. 



Years Unsprayed Sprayed Dusted 



New York 4 43..2 1L.4 12..2 



Michigan 4 7L.4 20..9 20..8 



Illinois _ .- 4 70..4 19..1 19..9 



Nova Scotia 4 5L.4 12..4 12..4 



Average of 16 56.. 5 15..6 15..6 



The above table contains the average for four years and includes years of 

 light and heavy scab infestation. However, since heavy infestations are the 

 most valuable tests the following data are quoted : 



Region Year Unsprayed Sprayed Dusted 



New York 1913 50..6 28..5 31-4 



1914 86..0 15..5 14..2 



Michigan 1915 100..0 49..1 58..2 



1917 99..9 14..1 10..5 



1919 62..4 15..2 12..6 



Illinois - 1915 67..5 9..0 7..0 



" 1916 68..4 0..9 14..7 



" 1917 81..8 28..4 27..1 



" 1918 67..6 37..8 30..9 



Nova Scotia 1919 90..8 21..1 11..4 



1920 51..4 29..7 40..0 



Average of 11 years 75..1 22..7 23..5 



