8 CIRCULAR 4 5 7, U. S. DEPARTMENT OF AGRICULTURE 



distribution of gas and also muzzles any flame that might otherwise 

 be forced into the house. 



The fumes from the sulfur did not cause appreciable corrosion 

 of the galvanized metal, of which the greater part of the burner 

 is composed, during the 3 years that it was in use. The iron frame 

 has corroded to a slight extent, but the burner will probably last for 

 a long time under ordinary conditions. 



The burner was designed to burn 32 pounds of flowers of sulfur, 

 this being the maximum dosage allowable in a standard mushroom 

 house of 16,000 cubic feet when at peak heat. With this dosage, flame 

 has at times been blown into the house through 10 feet or more of 

 pipe. When using the maximum dosage it has therefore been thought 

 best to cut down the speed of the fan by attaching one or two electric- 

 light bulbs to the line or by using a rheostat. By increasing the 

 length of lead-in pipe to 20 or 30 feet the same result might be ob- 

 tained, together with a cooling of the fumes. In empty houses ex- 

 cellent fumigations have been obtained with as little as 20 pounds 

 of flowers of sulfur. 



HEAT STERILIZATION 



In small spaces and where facilities are available, heat alone may 

 be used for the eradication of mushroom pests before the house is 

 filled. The source of the heat may be steam, or it may be electricity 

 if the current is very cheap. A temperature of 120° to 125° F., if 

 maintained for a few hours, should effectively rid the room of all 

 insect and mite pests. A 16-inch electric fan with the blades directed 

 upward at an angle of 45° should be kept running during this time 

 to distribute the air evenly, otherwise the top of the space will be 

 very hot and the air for a few inches above the floor will not be hot 

 enough to kill the insects and mites. The room should be as dry as 

 possible during this heating period. 



PEST CONTROL DURING PROCESS OF FILLING AND 

 HEATING OF BEDS 



When compost is placed in the beds a secondary fermentation 

 occurs and the temperature begins to rise. A small quantity of 

 manure in a large cool place will not heat up so well as a greater 

 quantity, nor will it raise the temperature of the surrounding space 

 greatly. If the filling occupies too much time, considerable heat is 

 wasted. For this reason the house should be filled as quickly as pos- 

 sible, the aisles swept out and cleaned of all loose manure, and the 

 doors closed tightly. Some growers fill a part of the house and wait 

 several days before filling the remainder. If manure is scarce, it is 

 better to form storage heaps until a sufficient quantity is obtained to 

 fill the house in one operation. 



Natural and Artificial Heating 



It is most important that a good heat be obtained in the compost at 

 the time the house is filled because heat is the mushroom grower's cheap- 

 est and best method of combating insects and other closely related 

 pests, as well as being necessary to "sweat out" the manure and put it in 



