MUSHROOM GROWING IN THE UNITED STATES 27 



the mushroom house with sulphur fumes or formaldehyde gas; dis- 

 infect the compost grounds by drenching with a solution of for- 

 maldehyde (1 pint of formalin to 15 gallons of water) or change the 

 composting grounds ; do not add soil to the manure or else change 

 the source of soil ; wet clown the spent mushroom soil at the time of 

 emptying to prevent the spread of spore dust; disinfect the truck 

 used to haul spent soil; avoid storing the manure, early fall crops, 

 running the spawn at high temperatures, and a wet, soggy condition 

 of the compost during fermentation in the pile or in the house. In 

 some cases soaking bed boards in disinfectant seems to have been 

 beneficial. Until more is known about the source of the infestation 

 and the conditions which favor it, all control measures must be con- 

 sidered tentative and no control program can be offered which will 

 assure the eradication of the disease. 



Another mold which sometimes penetrates deep into the beds is 

 known to the growers as "olive mold." It belongs to the Chaeto- 

 mium group and seems to be most serious in houses in which the 

 manure has been overheated in the beds. An organism called " brown 

 plaster mold " also is widespread, but it grows only under the side 

 boards and on the surface of the bed and after some delay mush- 

 rooms push up through it. 



INSECT PESTS 2 



The chief pests causing commercial damage to mushrooms are the 

 fungus gnats, mites, and springtails. 



In general, the fungus gnats of the genus Sciara cause the most 

 injury to the mushroom industry. They are prevalent in almost every 

 type of mushroom house or cave, since they usually enter in the com- 

 post when it is taken into the houses. The larvae or maggots of these 

 flies cause injury both by destroying the mycelium in the beds and 

 by feeding on the small mushrooms, which they completely devour in 

 many instances. These maggots can also render the large mush- 

 rooms unfit for market by tunneling upward through the stem and 

 cap. The adult flies often transport injurious mites which attach 

 themselves to the bodies of the flies from one mushroom house to 

 another and they also aid in disseminating some mushroom diseases. 



The mites, while not generally so prevalent as the fungus gnats, 

 are capable of causing serious losses once they become established in 

 mushroom houses. The mushroom mite proper, Tyroglyphus lintneri 

 Osb., feeds on the mushroom, producing dark pits which result in 

 decay, destroys the mycelium in the beds, and cuts off the feeder root 

 system so that the mushrooms do not mature, and decreased yields 

 result. 



It is much more widely distributed, apparently, than the mite, Lin- 

 opodes antennaepes Banks, which has also been found causing com- 

 mercial damage to mushrooms in several plants. 



Springtails cause very little damage to mushrooms in the East, but 

 are one of the most serious pests with which the growers operating in 

 the sandstone caves of the Northwest have to contend. While the 

 species found in the sandstone caves has never been described in the 

 United States and apparently is not present in the East, it is doubtful 



2 Prepared by O. E. Gahm. formerly assistant entomologist, Bureau of Entomology, 

 U. S. Department of Agriculture. 



