34 BULLETIN 1357, U. S. DEPARTMENT OF AGRICULTURE 
killing strength for the beetles and then to test the advisability of | 
using such measures on young and tender growth. For this pur- | 
pose preliminary experiments were carried out, in which from one- | 
fourth ounce to 2 ounces of sodium cyanide per 1,000 cubic feet of 
space was used. The results demonstrated that the adults could be | 
killed by fumigation at night with a 114 to 2-ounce dosage of the > 
sodium cyanide‘ and an exposure lasting two hours. | 
Fig. 15.—Greenhouse prepared for fumigation with hydrocyanic-acid gas 
After the first commercial test in which a killing dosage was 
used, an examination of the fumigated houses at 8.30 o’clock the 
next morning showed the following results: Large numbers of the 
beetles were found exposed on the surface of the foliage, lying on 
their backs and sides. Many were killed in the act of feeding, while 
others could be found lying on the surface of the soil and under- 
7A 1-114-3 formula was used, which required 1% fluid ounces of sulphuric acid (about 
1.84 sp. gr.), 3 fluid ounces of water, and 1 ounce of sodium cyanide (containing approxi- 
mately 51 per cent cyanogen) for each 1,000 cubic feet of space in the house. This was 
a slight divergence from the 1—-14%4-2 formula, and it was adopted in order to insure a 
more complete generation and equal distribution of the gas by providing a sufficient 
amount of dilute acid to submerge the cyanide, particularly in cases where only small 
quantities of the chemicals were being used in each generator. The quantities of mate- 
rials used at the respective rates of 14% and 2 ounces of sodium cyanide per 1,000 cubic 
feet were as follows: 
Sodium? cyanide. 2228 2 See eee 144 ounces, 
Sulphuric acid] 2 2a ee ee ee ee a eee ee 24%, fluid ounces. 
Waters. Sees 2 ee eee eee ee 4% fluid ounces. 
Sodium jcyanide <2 2= 222 28 sss ee ee See ee 2 ounces. 
Sulphuric:.acid= =.= 7 2323 ss Se ee ee See 3 fluid ounces. 
Water: bree fee ey Te ae ee a eee 6 fluid ounces. 
Further directions for the use of this gas are contained in Farmers’ Bulletin 880, 
entitled ‘Fumigation of Ornamental Greenhouse Plants with Hydrocyanic-Acid Gas,” 
wen ney be obtained by applying to the Office of Publications, U. S. Department of 
Agricuiture. 
