4 CIRCULAR 45 7, U. S. DEPARTMENT OF AGRICULTURE 



ficult to free from insect pests after these have become established. 

 Special care should be exercised to prevent the entrance of pests into 

 such places. In recent years a few growers in the United States 

 have been placing the composted manure in trays, which are then 

 put through a heat and fumigation in special rooms before being car- 

 ried into the caves or other growing rooms. Small crops grown by 

 amateurs in cellars and other suitable places about their homes are 

 particularly susceptible to insect attack, as these places are seldom 

 capable of being properly fumigated. The room where mushrooms 

 are to be grown should be separated from the rest of the building by 

 partitions insulated with sawdust or cork if possible, but in any case 

 made as tight as possible with building paper or other material. 



Between crops, the house, cellar, or other growing space should be 

 cleaned out thoroughly and the bedboards and supports scraped, 

 brushed, and washed. 



Spraying of the House 



About 2 weeks before it is filled with compost the house should be 

 sprayed inside to rid it of any insects, mites, or disease that might be 

 left over from the preceding crop. All bedboards and supports 

 should be included in this spraying. Several sprays have been in 

 use for this purpose, including the following : 



(1) Copper sulfate, at the rate of 6 pounds to 50 gallons of water. 



(2) Calcium hypochlorite, at the rate of 10 ounces to 50 gallons 

 of water. 



(3) Mercuric chloride, at the rate of 8 standard tablets to the 

 gallon of water or y 2 pound of crystals to 50 gallons of water. 



(4) Formaldehyde, at the rate of 2 gallons to 50 gallons of water. 



(5) Lime-sulfur, at the rate of 1 gallon of boiled lime-sulfur to 

 10 gallons of water. 



All these combinations are poisonous. Detailed safety instructions 

 for their safe handling should be secured from your State Depart- 

 ment of Agriculture or representatives of this Department before 

 their use is attempted. 



The best general-purpose spray for mushroom houses is the boiled 

 lime-sulfur, since this spray is an insecticide as well as a fungicide 

 and bactericide, which is not true of most of the materials men- 

 tioned above. 



In caves, and in some mine galleries where there is no danger of 

 setting the wooden bracing afire, flame throwers have been success- 

 fully substituted for sprays. The beds are first cleaned out. all loose 

 spent compost is swept up. and the flame is played over the walls, 

 ceiling, and floor, raising the temperature of these high enough to 

 preclude any possibility of insect survival. 



Fumigation or Sterilization of the House Before Filling It 



Immediately before the compost is brought in. the house should, if 

 possible, be fumigated with either formaldehyde or sulfur, or it 

 should be sterilized by heating. In caves, owing to poor ventilation 

 and ground beds, and in cellars, owing to the possibility of the gas 

 escaping, it is not always possible to do this. Formaldehyde is a good 



