JIUSHROOM PESXS AND THEIR CONTROL 



17 



bright yellow or orange, one-fourth inch or less in length. At times 

 these may appear in large numbers upon the casing soil and mush- 

 rooms, and if sufficiently numerous may cause injury to the spawn, 

 and to the mushrooms by eating small holes into the stems and caps. 

 Normally, however, these flies are minor pests of mushrooms. The 

 control measures given for mushroom and manure flies should be 

 effective against these flies also. 



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 mushroom mite (Tyroglyphus sp.) (fig. 6) frequently occurs 

 in enormous numbers in mushroom plantings and is capable of com- 

 pletely ruining the crop. The initial 

 infestation may be the result of intro- 

 duction of some stage of the mites into 

 the house with the compost, or upon 

 the clothing of workers or other per- 

 sons entering the houses, or upon the 

 bodies of various species of flies com- 

 ing from infested houses. 



This mite damages 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 of the spawn and may then 

 feed upon the manure itself, reducing 

 it practically to a mass of fine frass. 

 Mites feed in all except the egg and hy- 

 popial stages. Being so small, mites in 

 the mushroom beds are often overlooked. Unless they are very num- 

 erous 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 upon 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 

 nymph is a little larger than the larva and has eight legs instead of 

 six. After a longer period of feeding and after undergoing two 

 more molts the nymph becomes an adult mite. 



At times a migrating stage or condition occurs between two of 

 the nymphal molts, known as the hypopus. In the hypopial stage 

 the mite is flattened, with eight legs, rudimentary mouth parts, and 

 an area of suckers upon the ventral side. Not every individual 

 passes through this stage, and the conditions under which it is 

 formed are not well understood. Although unable to feed, the 



Figure 6. — Adult of a mushroom 

 mite, Tyroglyphus longior Gerv., 

 X 100. 



