86 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
cubic feet was used. The first exposure took place January 6, and the 
others on the following dates: January 20, February 9, March 1, 17, 
31, and April 21. The ventilators were so arranged that they could be 
operated from the outside and upon completion of the exposures they 
were opened for 15 to 20 minutes to permit the escape of gas. As is 
indicated in Table 1, which gives detailed information on the dosage 
and atmospheric conditions, the average temperatures in the greenhouse 
ranged between 58.2° F. to 65° F. for the wet bulb, and from 60.2° F. 
to 70° F. for the dry bulb, with an average humidity of 82%, while the 
outside temperatures were from 25° F. to 40° F. 
Table 1.—Dosage and Atmospheric Conditions on the Dates of Fumigation 
Date 
1922 
Amount of sodium 
cyanid per 1,000 
cu. ft. of space. 
Temperature in degrees Fahrenheit 
Relative 
Humidity 
Pet. 
Inside house 
Outside house 
Wet bulb 
Dry bulb 
Jan. 6 
24 ounce 
63.2 
69.5 
36 
71 
“ 20 
% “ 
63.3 
68.6 
40 
75 
Feb. 9 
y* “ 
— 
70.0 
34 
— 
Mar. 1 
“ “ 
— 
64.0 
25 
— 
“ 17 
* * «t 
64.0 
68.0 
42 
78 
“ 31 
11 t < 
62.4 
63.6 
44 
95 
Apr. 21 
(i *« 
58.2 
60.2 
41 
89 
Averages 
62.2 
66.2 
37.4 
81.6 
Results: While slight but only temporary burning occurred on such 
plants as jasminum, parlor ivy, marguerite daisy, ageratum, salvia, 
geranium, dahlia, cestrum, heliotrope, and stephanandro, no permanent 
injury followed. The insects referred to above were practically elim¬ 
inated with the exception of the mealybugs, and these were greatly re¬ 
duced in numbers by the repeated fumigations which killed off the imma¬ 
ture larvae. These results are significant since they indicate that many 
of the common greenhouse pests may be controlled in houses containing 
a miscellaneous collection of plants, by fumigating them at intervals, 
using a low concentration of gas, without any serious or permanent 
injury to the plants. 
Experiment ii. Control of the Fern scale, Hemichionaspis aspi- 
distrae (Sign.), and the Hemispherical scale, Saissetia hemisphaerica 
(Targ.) 
The results of another experiment indicate that with one exposure 
to the gas a house containing Nephrolepis bostoniensis in commercial 
numbers may be successfully fumigated using 1 ounce of sodium cyanid 
per 1,000 cubic feet of space with an exposure lasting 1 hour. 
The air space of this house was 35,000 cubic feet and the fumigation 
took place between 7 and 8 o’clock at night. The temperature readings 
; 
