REPORT OF THE SOCIETY 71 



Quebec, but the following figures arc for insects of great economic importance 

 here : 



.Variety Year Unsprayed Sprayed Dusted 



Alexander 1917 99..0 10..7 IL.O 



Duchess 1918 100..00 3..0 2..0 



Further it is very interesting to note that this year (1920) dusting for the 

 control of the apple maggot gave better results than any spraying results ever 

 obtained here. A mixture containing 45 per cent sulphur, 47 3^ per cent hydrat- 

 ed lime and IY2 per cent calcium arsenate, was applied on July 19th and on Au- 

 gust 5th. The dusted trees had less than 1 per cent of the fruit attacked, but 

 the check trees had from 50 per cent to 90 per cent of the fruit injured. 



Another very important consideration in comparing these methods is their 

 relative value in controlling sucking insects. In many fruit growing sections 

 this would probably be the most important phase of the subject; but in Quebec 

 it is by far the least important and hardl}^ needs consi.deration. It is only rarely 

 that aphids are present in sufficient numbers to be of economic importance and 

 the oyster shell bark louse could probably be held in check by dusting. 



One of the most difficult comparisons to make is that of cost, because pres- 

 ent day dusts are only experimental formulae and as this part of the work is in 

 such a rudimentary condition it is difficult to arrive at conclusions that are 

 satisfactory. However, the following figures are based on experimental work 

 done at Hemmingford : 



1917, sprajang, S16.09 ; dusting, $30.50. 



1918, spraying, $23.70 ; dusting, $40.40. 



1919, spraying, $27.58 ; dusting, $27.26. 



The above figures for 1917 and 1918 show dusting almost twice as costly as 

 spraying, whereas in 1919 the cost is practically the same. The cause of the 

 great reduction in the cost of dusting was in using a mixture in which the sulphur 

 and poison were greatly reduced and replaced by a cheap filler. If it were not 

 for severe russetting, in some seasons, of our best varieties, Fameuse and Mc- 

 intosh, Sanders' copper lime arsenic dust would be the cheapest to use, but 

 owing to this defect it is not advisable to use it for the calyx and later applica- 

 tions. 



The question of mixtures to suit the numerous conditions existing in various 

 parts of the country is a broad one. So far very little information is at hand, 

 but if the work of the past few years is continued with as much interest for the 

 next ten years, there w^ill probably be dusts equal to liquids for any condition 

 which might arise. 



