68 PROTECTION OF PLAINTS, 1920-21 



SPRAYING VS DUSTING 



C. E. Fetch, Dominion Entomological Laboratory, Hemmingford, Que. 



Sprajdng and dusting orchards have been carried on generally for several 

 years. In the case of spraying it is about forty j^ears and of dusting about ten 

 years. Therefore, the dusting S3'steni is working under the handicap of 30 

 years investigation and application. If the two systems had developed together, 

 it is impossible to state which would be the more efficient and popular. However, 

 we must judge between the two from the evidence at hand. 



In the preparation of this paper the writer was fortunate in having before 

 him an article by G. E. Sanders and A. Kelsall in the January issue of "Scientific 

 Agriculture." These writers covered the subject quite thoroughly and their 

 article will be followed fairly closely, but enlarged or criticised to suit Quebec 

 conditions. 



Dusting has many advantages over spraying, and if it were not for the 

 severity of black rot canker in Quebec, spraying might have no advantages over 

 dusting. In this age of high operating expenses speed is one of the main econ- 

 omic points to consider. Dust can certainly be applied much quicker than liquid 

 and the writer's results have shown dusting to be three or more times as fast 

 under similar conditions. This speed allows an application to be made at the 

 proper time, that is during the beginning of a humid spell or at the regular spray- 

 ing periods mentioned in the spray calendars. 



The first year that the writer dusted, the results were excellent for the 

 control of apple scab, in fact, better than with liquids and the applications were 

 made during the heat of the day. However, since then, results have not been 

 so good and it is probably due to dusting in the afternoon instead of in the morn- 

 ing or evening. The results of the first year indicate that dusting could be 

 done any time during the day and good results be obtained. The advantage 

 of the early morning and evening over the intervening period seems to have been 

 well established by other workers. The above observations show dusting to 

 be a time-saving method since dust is best applied during the part of the day 

 unfavorable to most farm work ; spraying on the contrary requires the best of 

 weather and the most important part of the day. The initial expense in pur- 

 chasing a dusting outfit is about one-half that of a sprayer and the upkeep is 

 considerably less. Sprayer parts soon become corroded and worn out, but the 

 chemicals in a dry state have little effect upon the duster. Therefore, the cost 

 of up keep is much less and the saving in time is also considerable, because, with 

 a sprayer, the broken parts are always discovered when it is in use. The most 

 important and busiest part of the spring is not time for delays and they are not 



