318 Report of THE DEPARTMENT OF ENTOMOLOGY. 
varying price of chemicals and the distance they have to be 
shipped. 
Johnson states that chemicals 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 peach tree 10 feet high 
by means of a tent, in our work cost 104 cents, while the chemi- 
cals for the same tree, when the 114 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 263 and 381 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 194 and 24 cents respectively for tents and fumigators. 
The foregoing does not include cost of outfit. Ata 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 344 cents. (Chemicals 104 cenis, 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 125 cents for tents and 18 cents for folding fumigators 
for trees 12 feet high. 
