U. S. DEPARTMENT OF AGRICULTURE 



Since it was not usually desirable to place insects in the houses dur- 

 ing fumigation, analyses were made to determine the concentrations of 

 gas obtained in the tests. The concentrations thus determined were 

 afterwards reproduced in a fumigation chamber and the effect upon 

 the insects and mites determined. 



MUSHROOM HOUSE FUMIGATION 

 MATERIALS AND METHODS 



The three sources of hydrocyanic acid, the fumigating gas, are 

 calcium cyanide, which is usually in granular form and from which 

 the gas is liberated when moisture is taken up from the air; sodium 

 cyanide, which is dropped into an earthen jar of dilute sulphuric 

 acid for the formation of the gas ; and liquid hydrocyanic acid, which 

 is a compressed form of the gas furnished in heavy metal cylinders. 



In order to attain a concentration high enough to be effective, the 

 gas must be generated as rapidly as possible. The fans need not be 

 removed from the house during fumigation with hydrocyanic acid gas, 

 and their operation assists materially in obtaining a rapid and uni- 

 form distribution of the gas. 



FUMIGATION WITH CALCIUM CYANIDE 



Calcium cyanide is used at from three-fourths to 1 pound per 1,000 

 cubic feet of air space, the heavier dosage being the more common. 

 The central alleyway of the house is lightly sprinkled if too dry, or 

 mopped drier if too wet, according to the judgment of the individual. 

 The cyanide is weighed out, placed in a pail or other receptacle, and 

 scattered as evenly as possible down the center alleyway of the house, 

 the operator walking backward toward an open door at the end of 

 the house as he distributes the material. In the case of a double house, 

 two men distribute the cyanide, starting at the far end of the central 

 alleyway of each house at the same time and timing their operations 

 so as to arrive at the doors of their respective houses simultaneously. 



FUMIGATION WITH SODIUM CYANIDE 



For fumigation by the " pot " or " hot gas " method, sodium cyanide 

 is used at the rate of one-half pound per 1,000 cubic feet of air space, 

 this dosage being approximately equal to 1 pound of calcium cyanide 

 per 1,000 cubic feet in the volume of hydrocyanic acid gas produced. 

 For a standard-size house (16,000 cubic feet), four glazed earthen- 

 ware crocks, each capable of holding a total of 3 gallons, were used 

 to generate the gas. The common formula of 1% fluid ounces of acid, 

 2 ounces of water, and 1 ounce of sodium cyanide was used. The 2 

 pounds of cyanide to go into each generator was weighed out (or, if 

 in egg or ball form of % or 1 ounce, counted out) and placed in a 

 heavy paper bag. Two quarts of water was put into each generator, 

 and the generators set at equal distances apart down the central alley- 

 way of the house. One and one-half quarts of a good grade of com- 

 mercial sulphuric acid (66° Baume) was then measured out for each 

 generator, and placed in a jar beside the generator. The bags of cya- 

 nide having been taken to the rear or far end of the house and left 



