EXrERlMENT STATION BULLETINS. 535 



DUSTING COMPARED WITH SPRAYING ORCHARDS. 



The practice of dusting orchard trees with sulphur and poison in 

 powder form, instead of spraying- them witli lime-sulphur or JJordeaux- 

 mixture has received the attention and consideration of fruit growers for 

 the past few years. The advantage of dusting as compared with spray- 

 ing is chiefly in the time saved and the ease of doing the work. 



For several years the Horticultural Section of the Experiment Station 

 has conducted tests to compare the results of dusting and of spraying. 

 These tests have been made in orchards in different sections and include 

 tlie standard varieties of apples. 



Tlie results in 1!>1T as stated in Special Bulletin No. 87 are quoted as 

 follows : 



"Dusting method gave very satisfactory results in 1917. The results 

 equaled those secured in the sprayed plots. The season was like that 

 of 1916 in that the infection periods were all early in the summer. The 

 control of scab on the fruit was very satisfactory in most plots. The 

 condition of foliage in the dusted plot at Muir was much better than on 

 the sprayed trees because of the spray injury on the latter. At Belding 

 there was little difference in the condition of the foliage of the two plots. 



At Morrice the foliage of the dusted trees was free from injury luit 

 showed some scab, while on the sprayed trees there was no scab but some 

 spray injury. 



"It is not possible to tell just why the results with dusting were so 

 much more satisfactory in 1917 than in previous years. This success 

 may liave lieen due to one or all of the following factors: Move el'licient 

 application of dust, iiner materials or more timely applications with 

 relation to infection periods. 



"Better results were obtained at Morrice and Muir where much of (lie 

 dusting was done when the trees were wet with i'illicn' rain or dew than 

 at Belding where the trees were always dry wlien mat<'rial was applied. 

 Several growers, however. Iiave secured satislaclory results by dusliiig 

 when tlie foliage was dry. 



"It is very (loubtfu! if the extra api>li«ation of dust made in July had 

 any l)enelicial eti'ect as weather conditions were not favrnable for scab' 

 inl'eetioji before the August ap|»lication.'' 



Tests were continued in 1918 but conclusive results were not secured. 

 Both the dusted and the sprayed trees produced good crops of line clean 

 fruit, and the check trees (those left unsprayed for comparison) had 

 only a small ])ercentage of fruits injured by scab, although tliey were 

 considerably damaged by the codling moth. 



Commercial fruit growers who have tried dusting instead of spraying 

 have had various experiences. No definite nor conclusive general results 

 can be drawn from these experiences, ilany of them are satisfied with 

 dusting while others will continue to use the sprays. 



We are compelled to state that the use of dusting material as a sub- 

 stitute for liquid mixtures is still in the experimental stage. 



