1918 ENTOMOLOGICAL SOCIETY. 79 



A FURTHER REPORT ON THE VALUE OP DUSTING VERSUS SPRAY- 

 , ING TO CONTROL FRUIT TREE INSECTS AND FUNGUS 



DISEASES. 



Lawson Caesak, Guelph. 



At our last annual meeting I gave an account of my e'xperience in 1916 in 

 dusting fruit trees with fine sulphur and arsenate of lead dust compared with 

 spraying with the liquid lime-sulphur and arsenate of lead. This year I again 

 carried out a similar series of experiments. 



Before giving my results for this year, it is perhaps wise to mention that this 

 new dust treatment has aroused a great amount of interest among fruit growers 

 and that they are anxiously waiting for definite knowledge as to its merits. 

 Hundreds of machines would be purchased at once if it were certain that dusting 

 were as satisfactory and reliable as spraying. The reasons for this are as follows : 

 (1) Dusting requires only about one-tenth the time in the case of large trees that 

 spraying requires. For instance, the total time for spraying a large 20-acre orchard 

 in any one season would be about three weeks, whereas the time for dusting would 

 be not more than three days. This would be a wonderful boon, especially when 

 labour is so scarce and costly, and when other important work such as cultivation 

 of soil is pressing. (2) Dusting can be done at almost exactly the right time, 

 which of course it is the duty of entomologists and plant pathologists to determine. 

 This means, for example, that one need never fail with dust to treat his trees lor 

 Codling Moth before the calyces have closed. With liquid spray it is often im- 

 possible in warm, good growing weather to do this. This promptness of applica- 

 tion is just as important for Apple Scab and enables the^ grower to wait until Ihe 

 blossoms or leaves are in just the right stage and yet make sure all will be treated 

 before they are too far advanced. (3) The outfit for dusting is not so heavy r.s a 

 power spray outfit and will go through wet ground where the latter would mire. 

 (4) Dusting is not nearly so dirty a job or so hard on clothes, Jace anl hands or 

 on horses and harness. It is true that at times it is hard on the eyes, but this can 

 be largely prevented by proper goggles and in any case it is £00n o\er and done 

 with. (5) There is no time spent in returning for fresh material and no time 

 worth speaking of lost in refilling. 



With all these advantages it is no wonder that the fruit grower hopes 

 dusting will take the place of spraying, though we may be sure he will ask about the 

 comparative cost. 



Comparative Cost of Dusting vs. Spkaying. 



We have not so accurate figures on the cost this year of dusting versus spray- 

 ing, but they lead to the same conclusion as last year's, namely, that on large trees 

 there is very little difference in cost between the two systems, whereas on smaller 

 trees the liquid is considerably cheaper, though much will always depend upon the 

 operator, as a careless man will be much more likely to waste dust than liquid. 



Some Changes in Methods of Applying the Dust and in the Material 



Itself. 



We used the same outfit this year as last, namely, the largest outfit sold by 

 the Niagara Brand Spray Co. For grapes we adied a short elbow to the pipe 

 with a long opening facing towards the side so that the dust could be driven in at 

 right angles or nearly so. 



