April, 1921. SCIENTIFIC AGRICULTURE 171 



Spraying vs Dusting 



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



(Paper given at the 13th Animal Meeting of the Quebec 

 Society for the Protection of Plants.) 



Ejirayiniv and dustiii<;- orcliards have been carried on are: (1) When fimgous diseases develop most rapidly 



generally for several years. In the case of spraying it the weather is most suitable for dusting but not for 



is about' forty years and of dusting about ten years, spraying; and, (2) the greater speed, which allows 



Therefore, the dusting system is working under the rapid treatment of large areas. 



handicap of 30 years investigation and application. If Aside from the above differences, it must be remem- 



the two systems had developed together it is impossible bcred that both systems mtist primarily be satisfactory 



to state which would be the more efficient and popular, for the control of fungous di.seases, biting and sucking 



However, we must judge between the two from the insects. Of the fungous diseases black rot canker and 



evidence at hand. apple scab are our two most important apple diseases. 



In the preparation of this paper the writer was for- As to the former, there is no evidence, to the writer's 



tunate in having before him an article by G. E. Sanders knowledge, to prove that dusting is or is not satisfac- 



and A. KeLsall in the January is.sue of "Scientific tory for its control but for the latter there is plenty of 



Agriculture." These writers covered the subject quite data to compare the two systems fairly satisfactorily, 



thoroughly and their article will be followed fairly The following figures are taken from Sanders' & 



closely, but enlarged or criticised to suit Quebec eon- Kelsall's article in Scientific Agriculture, Vol. 1, No. 1, 



ditionV. pp. 14-18. 



Dusting has manj- advantages over spraying, and if 



it were not for tlie .severity of black rot canker in Que- ^ Years. Uusprayed. Sprayed. Dusted. 



bee spraying might have no advantages over dusting. New York 4 43-2 11-4 12-2 



In this age of high operating expenses speed is one of Michigan 4 71-4 20-9 20-8 



the main economic points to consider. Dust can cer- Illinois 4 70-4 19-1 19-9 



tainly be applied much quicker than liquid and the Nova Scotia 4 51-4 12-4 12-4 



writer's results have shown dusting to be three or more Average of 16 56-5 15-6 15-6 



times as fast under similar conditions. This speed 



allows an application to be made at the proper time, The above table contains the average for four years 



that is during the beginning of a humid spell or at the and includes years of light and heavy scab infestation, 



regular spraying periods mentioned in the spray calen- However, since heavy infestations are the most valu- 



dars. able tests the following data are quoted : 



The first year that the writer dusted, the results were "** I 



excellent for the control of apple scab, in fact, better Region. Year. Unsprayed. Sprayed. Dusted. 



than with liquids and the applications were made dur- New York 1913 50-6 28-5 31-4 



ing the heat of the da.y. However, since then results " " ■■ .. 1914 86-0 15-5 14-2 



have not been so good and it is probably due to dusting Michigan 1915 100 49 1 58-2 



in the afternoon instead of in the morning or evening. " .... 1917 99.9 14.1 IQ-S 



The results of the first year would indicate that dusting " •• •• 1919 62-4 15-2 12-6 



could be done any time during the day an 1 good res It; Illinois 1915 67-5 9-0 7-0 



be obtained. The advantage of the ea-ly niorning and " 1916 68-4 0-9 14-7 



evening over the intervening period seems to have been " 1917 81-8 28-4 27-1 



well established by other workers. The above observa- " 1918 67-6 37-8 30-9 



tions show dusting to be a time-saving method since Nova Scotia- •• 1919 90-8 21-1 11-4 



dust is best applied during the part of the day unfavor- " " .. .. 1920 51-4 29-7 40-0 



able to most farm work; spraying on the contrary re- Average of 11 years- • 75-1 22-7 23-5 

 quires the best of weather and the most important part 



of the day. The initial expen.se in purchasing a dusting The above tables show neither system to have the 



outfit is about one-half that of a sprayer and the up- advantage when all the years were considered' but when 



keej) is considerably less. Sprayer parts soon become only the heavj' infestations are considered there is a 



corroded and worn out but the chemicals in a dry state slight difference amounting to -8 per cent in favor of 



have little effect upon the duster. Therefore, the cost spraying. At Henuuingford the following results were 



of upkeep is much less and the saving in time is also obtained in years of heavy infestation : 

 considerable because with a sprayer the broken parts 



are always discovered when it is in use. The most im- Year. Unsprayed. Sjn-ayed. Dusted. 



portant and busiest part of the spring is no time for de- 1917 SO-0 1-0 3-8 



lays and they are not infrequent where sprayers are 1918 95-0 -4 -4 



used. Furthermore, to replace broken sprayer parts 1919 93-0 20-5 62-3 



is a difficult and tedious job, owing to the awkward 



position in which many of the parts are located. With The above figures show both systeuis were satisfae- 

 dusters most of the jiarts are easily iiecessible. It is toi-y in 1917 and 1918 but decidedly otherwise for dust- 

 also true that the duster ready for action weighs less ing in 1919. There M-ere 3 daj'S separating the 3rd ap- 

 than a sprayer but this is not important in th(> majority plication in 1919. The spraying was done on the 17th 

 of Quebec orchards. and the dusting on the afternoon of the 20th. The 

 The two outstanding advantages in favor of dusting weather was as follows : 



