60 
The following papers were then presented: 
HYDROCYANIC-ACID GAS AS AN INSECTICIDE ON LOW-GROWING 
PLANTS. 
By E. Dwieut Sanperson and C. L. Penny, Newark, Del. 
The desirability of using a gas as an insecticide upon low-growing 
plants, more especially for plant lice, but also for some leaf folders 
and other insects which can not be reached by means of a spray, has 
long been apparent to entomologists. 
So far as known the only work previously done upon this problem 
is that of Prof. H. Garman, who seems to have been the first to sug- 
gest such use of a gas, with carbon bisulphide upon the melon louse, 
mentioned at the meeting of this society in 1893, and his subsequent 
experiments with hydrocyanic-acid gas in 1894 (Bul. 53, Ky. Agr. 
Exp. Sta.), and the further ex <periments Of Dir) SB: Smith with car- 
bon. bisulphide upon the same insect in 1895 (Bul. 109, N. J. Agr. 
Exp. Sta.). Itis believed that neither of these gentlemen, however, 
have perfected practical apparatus, nor outlined a method for its 
extensive use in the field 
Two years ago, under the direction of Prof. W. G. Johnson, we did 
considerable work with hydrocyanic-acid gas in tents and box frames 
over trees, and in boxes for nursery stock, in combating the San Jose 
scale. In one instance several hundred young trees were fumigated 
with flour barrels. Young apple trees were also fumigated for plant 
lice with marked success. Having read the experiments by Protrecuns 
Garman and Smith, this experience with the gas led me to attempt the 
problem of naling it to use upon low- Sgn plants during the 
past spring. 
Carbon Wena has not been tried, as the trials already made, 
including also some recently recorded by Professor Webster, showed 
that it was very much slower in its action, a serious obstacle to its 
extensive use. This point might indeed bé overcome by using a larger 
number of coverings, but a large investment in apparatus would pre- 
clude its use in many instances. Where carbon bisulphide requires an 
hour to kill plant lice, hydrocyanic-acid gas takes but ten minutes. 
Thus in use upon melons, with a cover for each plant, with 100 covers 
hardly more than 1,000 plants could be fumigated in a day with carbon 
bisulphide, while five or six times as many could be treated with hydro- 
cyanic-acid gas. As regards cost of chemicals there is not much differ- 
ence, thor ugh, if anything, carbon bisulphide is slightly more expensive. 
Both gases are dangerous poisons, but, all things considered, I believe 
that hydrocyanic-acid g gas is possibly preferable to carbon bisulphide 
in this respect. There is but little danger with hydrocyanic-acid gas in 
such small quantities in the open air, the greatest danger being in 
