102 



and the doors and ventilators were kept open for several days, so as 

 to allow it to become as warm as possible, in order to render the 

 larva? more active. 



The maximum temperature from April 25 to May 12, the date 

 when the house was fumigated, was 84° and the minimum 33° F. 

 May 11, the night before the treatment was applied, the thermometer 

 dropped to 33°, but rose rapidly the following day, registering 

 80° F. in the afternoon. 



Before charging the house, my assistant, Mr. Swezey, who was sent 

 to do the work, examined many cocoons, and active larvse, but no 

 pupa3, were found. 



The formula used was 1 ounce of potassium cyanide 98 per cent 

 pure, 1 fluid ounce of sulphuric acid, and 3 fluid ounces of water to 

 each 100 cubic feet of space. As the house measured 32 by 24 by 14 

 feet, 6^ pounds of cyanide were required; this was divided into 

 three equal parts and placed in separate jars. The ventilators were 

 tightly closed and the house charged at 3 p. m., and the door was 

 opened at the expiration of twenty hours. The odor of gas was then 

 very strong, and, after airing for one hour, Mr. Swezey made an ex- 

 amination of cocoons taken from several boxes. Sixty-nine worms 

 were removed and placed in a jar, and as about one-third of these 

 showed signs of life when they were taken the house was closed and 

 allowed to remain so for over a week. 



An examination of the w^orms in the jar, which was made five hours 

 after they were taken, showed that 39 were alive and 30 were appar- 

 ently dead. A final examination made June 9 gave the following 

 data : 28 worms and 3 pupse dead, and 1 larva, f) pupcT?, and 23 moths 

 alive. Eight larvse had escajjed from the jar. 



Taking this count as a basis, it is evident that the gas killed less 

 than 45 per cent of the worms. In removing the larvse from the 

 boxes, it was almost impossible to prevent injuring the cocoons, and 

 in many cases the larva-; placed in the jar left the old cocoons and sj)un 

 entirely new ones. This would undoubtedly have some influence on 

 the death rate, and under normal conditions, where the cocoons were 

 midisturbed, the treatment would not be as effective as in this instance. 



An examination of cocoons in the fruit house May 26 showed that 

 less than 40 per cent of the larva? were dead, although the house had 

 been tightly closed since the day it was first aired out, and the odor of 

 the gas was still very perceptible. Computing the price of the cyanide 

 at 30 cents and the acid at 5 cents per pound, the cost of this treatment 

 was $2.36. Had it been efi'ective in destroying the larvae it would 

 have furnished a simple and comparatively cheap method of treating 

 fruit houses and would have been preferable to the iise of screens on 

 the doors and ventilators, Avhich are liable through carelessness or 

 accident to be left open and give the moths an opportunity to escape. 



