264 Journal of Agricultural Research voi. xv. No. s 



EXPERIMENTS TO DETERMINE THE POSSIBILITY OF KILLING INSECTS 

 BY FUMIGATION WITHOUT REMOVING THE PLANTS FROM THE CON- 

 TAINER 



To determine the effectiveness of this method of fumigating, the insects 

 and plants were exposed to the gas under conditions comparable to those 

 existing at commercial vacuum fumigation plants, where time would not 

 permit the removal of the plants from the containers. To obtain this 

 result, pyralid lar\^ge were fumigated as follows: Two in a vial plugged 

 with cotton; two secreted in the roots of a cattleya wrapped in one 

 thickness of newapaper; two secreted in the roots of a cattleya wrapped in 

 cardboard and three thicknesses of newspaper; one in a vial plugged with 

 cotton and wrapped with plant in two thicknesses of manila paper; two 

 in nests of two and three pill boxes/ respectively. 



The containers were placed in the fumigation chamber, the door closed, 

 and a 20-inch vacuum produced. The gas was then generated, a dosage 

 of I ounce of sodium cyanid ^ per 100 cubic feet of space being given, with 

 an exposure of 40 minutes as follows : Five minutes were allowed for full 

 generation and then 5 minutes to wash all the gas over to the fumigation 

 chamber, after which the plants and insects were exposed to the gas for 

 30 minutes under normal atmospheric conditions. At the completion of 

 the exposure the gas was removed from the fumigation chamber by pro- 

 ducing a 25-inch vacuum. Upon examination all larvae were found 

 dead, irrespecive of their position, some being flattened out and void of 

 viscera. 



To determine further the penetration of hydrocyanic-acid gas under 

 vacuum conditions, the following test was conducted with the black- 

 walnut worm {Datana iniegerrima Grote and Robinson). This experi- 

 ment differed slightly from the former in that the exposure was increased 

 to one hour with a preliminary vacuum of 26 inches. The dosage re- 

 mained the same, the larvae being exposed to the gas under the following 

 conditions: (i) Eight larvae in a nest of triple pill boxes, inclosed in two 

 tight-fitting cardboard coccid boxes,^ the outer, or larger, box being 

 wrapped with four thicknesses of dry newspaper and one layer of heavy 

 wrapping paper and tied. This package was then placed in a wheat sack 

 which was inclosed in a mail bag. (2) Four larvae were similarly wrapped, 

 except that the newspaper was thoroughly wet. (3) Four larvae in triple 

 pill boxes were inclosed in a tight-fitting screw-top maiUng tube and 

 placed in a thin seed sack ^vithin a wheat sack. (4) Same conditions as 

 No. 3, except that the mailing tube was wrapped in six layers of wet news- 

 paper. Upon completion of the exposure all larvae were dead, whereas 

 all larvae similarly wrapped and held as controls were alive. 



' Diameter of pill boxes as follows: iH. iJ^, and iK inches. 



2 Sodium cyanid guaranteed to contain not less than 51 per cent cyanogen and commercial sulphuric add 

 (about 1.84 sp. gr., or 66° Baume) were used in all experiments referred to in this paper. 

 ' These boxes measured 5 by 3 by 2 and 3 by 2 by i'4 inches. 



