318 Keport of the Department of Entomology. 



varying price of clieniicals and tbe distance tbey Lave to be 

 shipped. 



Jolinson states that cliemicals cost from six to seven cents for 

 trees 12 to 17 feet high. Apparently this estimate is based on 

 pear trees. 



By using a uniform charge of .25 gram of potassium cyanide 

 per cubic foot and one and a half times as much acid by volume, 

 the chemicals to fumigate a low-grown i)each tree 10 feet high 

 by means of a tent, in our work cost 10| cents, while the chemi- 

 cals for the same tree, when the 11^ foot folding fumigator was 

 used, cost 15 cents. 



With an outfit of four tents or four folding fumigators, the 

 labor required to fumigate a tree cost 16 cents, making a total 

 of 26^ and 31 cents per tree respectively. The expense of labor 

 in each case is based upon the cost of one head operator and 

 four helpers all employed by the day, also on condition that this 

 force fumigate fifty trees in a day of ten hours, allowing 40 

 minutes for each tree. It was estimated that with an outfit of 

 six tents or the same number of folding fumigators, the same 

 force could fumigate 90 trees in a day, in which case the cost of 

 labor per tree would have been reduced to 9 cents each, or a 

 total of 19| and 24 cents respectively for tents and fumigators. 



The foregoing does not include cost of outfit. At a rough esti- 

 mate six tents costing |150 could by patching and re-oiling be 

 made to last long enough to fumigate one thousand trees. 

 Hence the cost of outfit for each tree would be 15 cents making 

 a total cost per tree of 34^ cents. (Chemicals 10| cents, ap- 

 paratus 15 cents and labor 9 cents.) The total cost per tree 

 cannot be computed on same basis for folding fumigators, for 

 with the same amount of patching and care in handling, the 

 latter would last indefinitely. 



As shown under " Absorption of Gas " it is best in orchard 

 fumigation to use at least .30 gram of potassium cyanide per 

 cubic foot of space, or about one ounce for every 100 cubic foot. 

 The cost of chemicals will be proportionately increased, being 

 about 12^ cents for tents and 18 cents for folding fumigators 

 for trees 12 feet high. 



