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BTJUjETIlir 1351, U. S. DEPARTMENT OF AGRICULTUEE 



killiiig 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 

 Inlled by fumigation at night with a l^^ 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- 



'' A 1-1 1^-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 1-1 %-2 formula, and it was adopted in order to insure a 

 more complete generation and equal distribution of the gas by providing a suflacient 

 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 1% and 2 ounces of sodium cyanide per 1,000 cubic 

 feet were as follows : 



Sodium cyanide 1% ounces. 



Sulphuric acid 2% fluid ounces. 



Water 4% fluid ounces. 



Sodium cyanide 2 ounces. 



Sulphuric acid 3 fluid ounces. 



Water 6 fluid ounces. 



Further directions for the use of this gas are contained in Farmers' Bulletin 880, 

 entitled " E\imigation of Ornamental Greenhouse Plants with Hydrocyanic-Acid Gas," 

 which may be obtained by applying to the Office of Publications. U. S. Department of 

 Agriculture. 



