January, 1921. 



SCIENTIFIC AGRICULTURE 



15 



4. — Lower cost of machinery. 



The initial cost of a crusting outfit is two-thirds that 

 of a sprayer, tlie cost of upkeep is less, the gasoline 

 used is less, and the duster is a longer-lived machine. 



5. — Lighter weight of dusting apparatus. 



A dusting outfit with dust and operatoi-s docs not 

 weigh more than a third of the weight of a sprajer 

 ready for operation, so that in spring it can be taken 

 over hills or over wet ground ujkju which a sprayer 

 would mire. 



6. — Less liability to trouble and breakdown. 



A dusting outfit in practice is a reliable machine and 

 is not responsible for delays due to leaky valves, blow- 

 outs, etc., which always occur witli a higli pressure 

 sprayer. 



7. — The simplicity and speed of a tliister makes a 

 greater appeal to the grower. 



More growers will dust than will spi-ay, even if the 

 total cost is the same, because it is less trouble. This 

 is highly important, particularly in an orcharding 

 comjnuuity, where it is desirable in the interest of 

 every individual to improve the standard of product 

 of the entire community. 



Of all these advantages the first and last named are 

 probably the most important. As before stated the.se 

 advantages are generally recognized by all. Why then 

 the doubts about the status of dusting? These may 

 be stated: 



1. — Doubts as to the efficiency of dust in controlling, 



(a) Fungous diseases. 



(b) Biting insects. 



(c) Sucking insects. 



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2.— Doubts as to the relative total cost. 

 Experimental Data. 



Let us examine the experimental data available on 

 tlie relative efficiency of sprays and dusts. Tables 

 1, 2 and 3, referring to the United States, are taken 

 from the previously mentioned work of Prof. Whetzel. 

 All experiments that are reasonably comparable have 

 been included, where such exi)eriments have been ex- 

 pressed in tabular form. The tables are pre.sented here 

 without comment, but for detailed explanations the 

 original paper of Prof. Whetzel should be consulted. 



To come now to experimental data in Canada, most 

 results are reported in form not readily tabulated. In 

 the proceedings of the Entomological Society of 

 Ontario for 1916 and 1917, Professor L. Caesar (of 

 Ontario) and Mr. C. E. Fetch (of Quebec) both pre- 

 sent results on dusting. To quote from Prof. Caesar's 

 results of 1916, he says: '-On each of the plots apple 

 scab was well controlled. Tlie liquid-sprayed part was 

 a little better than the dusted, but not much. There 

 is no doubt that fully 99 per cent of the fruit on the 

 lime-sulphur and arsenate of lead plot was free from 

 scab. The dusted part averaged, as nearly as we 

 could judge, 97 per cent." 



'•Checks.— On the mountain side Baldwin trees aver- 

 aged approximately 50 per cent scabby fruit, Golden 

 Russets approximately 10 per cent. An examination 

 of nmny trees throughout the district lead us to estim- 

 ate that ni general, unsprayed Spy trees were about 60 

 per cent infested with scab, Greenings and Baldwins 

 about 40 per cent." 



"Codling Moth.— My estimate made the first week 

 in October for the total of the fruit both on the trees 

 and on the ground was that it ran somewhere between 

 5 and 10 per cent with an average of probablv 8 per 

 cent. There was very little difference between the 

 different plots." 



"Check trees and poorly sprayed orchards nearbv 

 varied ^from 30 per cent to 80 per cent wormv with 

 about 75 per cent of these entering at the calyx end. 

 It IS quite clear, therefore, that the dusting will control 

 the codling moth satisfactorilv." 



Of results in 1917 he .says: "In both liquid and dust 

 portions on all varieties, even on Snow, there was less 

 than 1 per cent scab. A snow tree in a neighboring 

 orchard across the fence had over 90 per cent of scab 

 and Bald^vin and Greenings in it averaged about 50 

 per cent scab." Professor Caesar, however states 

 that he is doubtful about obtaining the same results 

 under different conditions. 



Fetch states of results in 1917: "This year was a 

 very bad .year for scab and we dusted and" sprayed in 

 order that we might test out both methods. The re- 

 sults were 99 per cent clean fruit on the spraved por- 

 tion and 97 to 98 per cent on the dusted portion. It 

 was all done in one orchard, side by side, taking 90 

 trees in each portion." 



Professor W. II. Brittain (of Xova Scotia) has con- 

 ducted numerous dust experiments during the past 

 several years. The results were never published, but 

 his remarks based on. them may be found in the last 

 several Annual Reports of the Nova Scotia Fruit 

 Growers' Association. In the 1920 Report pp. 79 and 

 80, Profe.ssor Brittain states: "In 1917 at the Annual 

 Meeting of the Nova Scotia Fruit Growers Associa- 

 tion, I summed up our experiments in Spraying vs 

 Dusting as follows: 



