NOV 2 7 1935 



CIRCULAR No. 364 NOVEMI 



UNITED STATES DEPARTMENT OF AGE 

 WASHINGTON, D.C. 



C*f~J\ 



1 



CYANIDE FUMIGATION OF MUSHROOM HOUSES 



By A. C. Davis, assistant entomologist, Division of Truck Crop and Garden In- 

 sect Investigations, and H. V. Claborn, assistant scientific aide, Division of 

 Insecticide Investigations, Bureau of Entomology and Plant Quarantine 



CONTENTS 



Introduction 



Mushroom house fumigation 

 Materials and methods 

 Distribution of the gas_ 



Page 



1 

 2 

 2 



Page 

 Fumigation tests on insects and mites_ 6 



Apparatus and methods 6 



Results obtained 7 



Summary and conclusions 9 



INTRODUCTION 



It is the general practice among mushroom growers to fumigate 

 the houses when the maximum temperature, or " peak heat ", has 

 been reached in the freshly filled houses, on the theory that the in- 

 sects not killed by the excessive heat of the compost will be driven 

 to the surface wiierg they will be exposed to the fumigants. During 

 the period^T secondary fermentation of the compost in mushroom 

 beds, which is customarily referred to as the " heat ", the air tem- 

 perature of-ar mushroom house may reach from 120° to 140° F. at the 

 ceiling, from 100° to 120° at the level of the bottom beds, and from 

 90° to 108° at the floor level, the compost in the beds being even 

 hotter; and fans are used in an effort to equalize the temperature. 

 The relative humidity is usually around 90 percent at this time. 

 The compost in the beds, the false ceiling, the walls, and the floor 

 are very moist. 



Under such conditions of heat and moisture, hydrocyanic acid gas is 

 absorbed from the air with great rapidity. This absorption, however, 

 has little or no harmful acidifying effect on the surface of the compost. 

 Furthermore, the average mushroom house is so constructed that it 

 is difficult, if not impossible, to seal it tightly, so leakage is more or 

 less unavoidable. 



Investigations were therefore undertaken in the mushroom-growing 

 center about Kennett Square, Pa., and at Arlington Experiment 

 Farm, Va., for the purpose of comparing the concentrations of hydro- 

 cyanic acid gas obtained with the three most common methods of 

 generation, and to determine its effectiveness, under conditions en- 

 countered in the houses at peak heat, against the insects and mites that 

 attack mushrooms. 



144250—35 



