MUSHROOM PESTS AXD THEIR CONTROL 



21 



Dusting is effective against the adults, but has little effect on the 

 larvae. Other insecticides tried to date are not of much value. 



Larvae on the surface of the casing soil have been successfully con- 

 trolled by allowing the beds to dry out somewhat between flushes and 

 then drenching the surface with boiling water. Playing an alcohol 

 or gasoline blowtorch rapidly over the surface seems not to damage 

 the spawn, and will probably kill as many larvae as the hot water. 

 Neither of these methods will kill larvae below the top one-eighth or 

 one-fourth inch of casing soil. Gasoline torches should be used with 

 caution because of the danger of oil fumes causing "rose-comb" mush- 

 rooms later on. 



Mites 



Four species of mites are important pests of mushrooms, one very 

 serious, two less so, and the fourth sporadic and of minor importance. 



THE MUSHROOM MITE 



The species Tyroglyphus lintneH Osb. (fig. 8) is the one most 

 frequently found in mushroom houses in the United States. This 

 mite feeds on almost any organic material, and is common upon 

 cheese, dried meat, and fruits. It has 

 been reported only from the United 

 States and Canada. It frequently oc- 

 curs in enormous numbers in mush- 

 room plantings and is capable of com- 

 pletely ruining the crop. The initial 

 infestation may be the result of the in- 

 troduction of some stage of the mites 

 into the house with the compost, or on 

 the clothing of workers or other per- 

 sons entering the houses, or on the 

 bodies of various species of flies com- 

 ing from infested houses. 



The mites damage mushrooms by 

 eating holes into their caps and stems 

 in the button stage, preventing them 

 from developing or rendering them un- 

 marketable, and in eating the mycelial 

 threads in the spawn. If these mites 

 become very numerous they may con- 

 sume all the spawn and may then feed on the manure itself, reducing 

 it practically to a mass of fine frass. Mites feed in all except the egg 

 and hypopial stages. Mites in the mushroom beds are often overlooked, 

 as they are very small. Unless they are very numerous the damage to 

 the mushrooms may be slight, and the damage to the spawn is reflected 

 only in smaller yield, which may often be attributed by the grower to 

 other causes. 



The eggs are extremely small, although rather large as compared 

 to the parent mite. They are oval, white or yellowish, and are laid 

 in the spawn or casing soil, or on the mushrooms. In from 8 to 14 

 days the egg hatches into a very small, white, six-legged larva. In 

 another 8 or 10 days the larva molts and becomes a nymph. The 



Figure 8. — Adult of a mushroom 

 mite, Tyroglyphus lintneri 

 Osb., X 100. 



