214 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
received their replies they totaled an almost unbelievable sum; so I cut 
it in half and sent it to the Secretary of Agriculture. The amount was 
so much larger than that sent in by any other Bureau that the Secre¬ 
tary in turn cut my sum in half. When the report went to the chairman 
of the committee, he cut in half the amount submitted by the Secre¬ 
tary for the Bureau of Entomology. So the amount finally printed was 
one-eighth of the original estimate. However, since that date such 
great work has been done that I am sure that the original estimate that 
came to me from branch chiefs is by far nearer the truth than the figure 
published. 
President A. G. Ruggles: The next paper is by E. R. Sasscer and 
C. A. Weigel. 
RECENT DEVELOPMENTS IN GREENHOUSE FUMIGATION 
WITH HYDROCYANIC-ACID GAS 
By E. R. Sasscer, Collaborator, and C. A. Weigel, Entomologist, Greenhouse In¬ 
sects Investigations, Bureau of Entomology, Washington, D. C. 
Abstract 
A simple device adapted for simultaneously dropping cyanide into generators was 
developed and proved practical in commercial greenhouses, Liquid hydrocyanic 
acid (equivalent to ounce NaCN per 1,000 cubic feet) was effective against several 
species of aphids, white fly, and scale insects, but it can not yet be safely recommended 
for use by the average florist. Further data on plant tolerance of Kentia and Areca 
palms for HCN fumigation is presented. At low temperature, 1 ounce NaCN per 
1,000 cubic feet was not effective against the eggs of Pseudaonidia duplex (Ckll.). 
Miscellaneous data on insect control with HCN is given. Preliminary notes on the 
use and effectiveness of calcium cyanide indicate that it may become useful as a 
greenhouse fumigant. 
While experimenting with liquid hydrocyanic acid to determine its 
value for greenhouse fumigation a slight modification of the device 
employed for liberating the liquid was found to be useful and applicable 
for fumigating with the pot method as well. The very rapid volatiliza¬ 
tion of liquid hyrdocvanic acid due to the high temperatures that nor¬ 
mally" prevail in greenhouses necessitated the development of some 
method of insuring safe liberation and uniform distribution of the gas. 
After some preliminary experimentation it was found that the “appli¬ 
cator” as used in California was not so w^ell adapted to greenhouse 
purposes. The length of the commercial type of houses would ne¬ 
cessitate the operator stopping at several points in the house in the 
application of the liquid and would thus expose him directly^ to the 
