JOURNAL OF ECONOMIC ENTOMOLOGY 
294 
[Vol. 11 
California State Commission of Horticulture that he found an infes¬ 
tation on Amaranthus. 
A. F. Swain : I think it was only an accidental infestation. 
President G. P. Weldon: The next paper on the program is by 
H. J. Quayle, entitled “Cyanide Fumigation: Diffusion of Gas Under 
Tent and Shape of Tree in Relation to Dosage.” 
CYANIDE FUMIGATION 1 
Diffusion of Gas Under Tent and Shape of Tree in Relation 
to Dosage 
By H. J. Qtjayle 
The practical query “is there a better killing of scale insects secured 
at the top than at the bottom of the tree,” in citrus fumigation, sug¬ 
gested the following experiments. More or less serious injury some¬ 
times occurs in the top of high trees. If the dosage is reduced to 
avoid this injury, the question then arises as to the effectiveness of 
the reduced dosage in all parts of the tree. 
Citrus trees vary considerably in shape from the low broad lemon 
tree to the tall narrow seedling orange tree. In one case the extreme 
may be a tree whose circumference is twice the distance over the top, 
while in the other the circumference and the distance over the top may 
be equal. 
It may be possible to determine the concentration of the gas in dif¬ 
ferent parts of the tent by chemical means, but this would be a tedious 
method and might be difficult to apply for the period of 45 to 60 min¬ 
utes which would be necessary. Consequently, we chose to determine 
the concentration of gas in different parts of the tent by entomological 
rather than by chemical methods. This was done by determining the 
killing effect on insects placed in different parts of the tent. 
Likewise the relation of the shape of the tree to the dosage was de¬ 
termined by a series of experiments in which the same amount of gas 
was generated under two tents representing the extremes in shape. 
Form “trees” were constructed over which were placed ordinary 
fumigation tents of 8 ounce U. S. A. duck. The dimensions of the two 
trees were 31 ft. x 31 ft. and 22 ft. x 44 ft. They were thus fair sized 
trees, and the conditions were practically normal, excepting that there 
was no foliage under the tent. This point, however, has no bearing on 
the results, for comparatively the same conditions prevailed in both 
1 Paper No. 48. University of California, Graduate School of Tropical Agricul¬ 
ture and Citrus Experiment Station, Riverside, California. 
