36 PROTECTION OF PLANTS — 1922-23 



cause for some pretty serious thought in these differences. Are the experi- 

 menters falling down in their dusting operations ? Are the experiments not 

 being conducted in a way that makes the results applicable to orchard condi- 

 tions? Or are the experiment station men doing their spraying much better 

 than the farmer and doing their dusting no better than the farmer ? 



Personally, I think that the greatest cause for these differences is the fact 

 that the average farmer will, if anything, both time his dusting better and 

 apply his dust better than the experimental men, and when spraying he will 

 not do anything like so thorough a piece of work 



The big objection to dusting has in the past been the cost of materials. 

 Everyone agreed that dusting saved eighty percent of the time of application, 

 the initial cost and depreciation of the machinery was lower and the life of 

 the machine twice as long, the weight of the machine much less, making it 

 more desirable on both hilly and wet ground, and the results obtained satis- 

 factory to farmers. The price of dusting material has in the past been high, — 

 about double the cost of spraying material, and has been the one big obstacle 

 to the spread of the method. In 1918, the introduction of Blue Copper Arsenic 

 dust, which is made up of monohydrated copper sulphate, hydrated lime and 

 arsenate of lime, lowered the cost of dusting materials so that, reckoning the 

 saving in time and equipment, the total cost of dusting was brought below 

 the cost of liquid spraying. This year, for the first time in the history of dusting 

 two dusts are on the market that cost the grower about the same as the mate- 

 rials for liquid spraying. These are what we term Brown Copper Arsenic 

 dust and Green Copper Arsenic dust. 



Brown Copper Arsenic dust in the formula 43^-2, which is used on apples, 

 contains 18 lbs. of copper sulphate crystals and 8 lbs. of arsenate of lime in 

 the hundred, the remainder being made up of hydrated lime. Green Copper 

 Arsenic dust, in the formula 9-5, which is used on potatoes, contains 36 lbs 

 of copper sulphate crystals and 5 lbs. of metallic arsenic in the form of arsenites , 

 or the equivalent of either twenty-five pound of arsenate of lead or twenty 

 pounds or arsenate of lime in the hundred, the remainder being made up of 

 hydrated lime. These dusts are being retailed in both Canada and the United 

 States at approximately the same price as the farmer can buy the equivalent 

 amounts of copper sulphate, lead arsenate and lime for making liquid Bor- 

 deaux, thus making dusting materials, for the first time, as low or lower in 

 price than the materials for liquid spraying. This removes the greatest 

 single objection to dusting. Both these dusts will be largely used commer- 

 cially this season and their exact status as fungicides and insecticides deter- 

 mined. 



