Farmers' Bulletin 780 



at 55° F. or to roduce it to that tem- 

 perature ui>on indications of attack by 

 maggots, damage by these pests is 

 easily controlled. Otherwise it is evi- 

 dent that, in the control of the mush- 

 room maggots, measures should be 

 undertaken early in the season for 

 their elimination from the mushroom 

 house and precautions observed 

 against their subsequent entrance. 

 These precautions should begin with 

 the construction of the house or cellar. 

 The building should be so constructed 

 as to permit of effective fumigation 

 and should be fitted with tight screens 

 of fine wire gauze, suitable to prevent 

 the ingress of the fungus gnats. The 

 gnats may also be brought into the 

 house through the agency of the ma- 

 nure used in the beds, esi>ecially if 

 the compost is carelessly prepared. 

 In large commercial houses the care 

 taken to secure uniformity in the fer- 

 mentation of the compost renders im- 

 probable any danger from this source, 

 since a uniform heat of 150° F. or 

 more is frequently attained in the 

 process, this being sufficient to destroy 

 maggots and other pests which may 

 l)e present. Fumigation with carbon 

 disulfide just previous to spawning is 

 also productive of good results in de- 

 stroying maggots in the compost. The 

 disulfide should bo used at a strength 

 of 2 to 4 pounds to 1.000 cubic feet of 

 space and should be evaporated in 

 shallow pans placed in the highest 

 part of the house. The liberated vapor 

 of carbon disulfide is very inflamma- 

 hle and irlien mixed irith air is ex- 

 plosive if brought into contact with 

 fire or sparks, so that care should be 

 used to avoid bringing any fire into 

 the building during the process of 

 fumigation. 



One of the best methods for the 

 destruction of the adults or laies in 

 their occurrence in mushroom houses 

 is fumigation with tobacco or nicotine 

 preparations, such as are used in 

 greenhouses. These should be used in 

 accordance with the directions indi- 

 cated on the package for a medium or 

 heavy fumigation.' Used in this man- 

 ner and applied once a week during 

 the bearing season of the mushroom 

 bed, this method has been so succe.ss- 

 ful in reducing the number of flies 

 that very little damage, if any, re- 

 sulted from the larvje. 



Hydrocyanic-acid gas is an effective 

 fumigant against these pests where a 



good system of ventilation is provided. 

 The most satisfactory dosage is at the 

 rate of 3 ounces of sodium or calcium 

 cyanide to each 1,000 cubic feet of 

 space. The fumigation should be ap- 

 plied while the atmosphere of the 

 house is relatively dry, for if under- 

 taken immediately after the beds have 

 been sprinkled down some burning of 

 the crop may I'esult. A good practice 

 is to fumigate two or three times a 

 week over a period of two weeks, re- 

 leasing the gas in the evening and ven- 

 tilating the houses before sprinkling 

 dow'n the following morning. As the 

 gas is extremely poisonous, the opera- 

 tor should familiarize himself with 

 the necessary precautions to be ob- 

 served in its application, as outlined 

 in Farmers' Bulletin 880 on green- 

 house fumigation. Several large com- 

 mercial mushroom growers have re- 

 ported material benefits from the es- 

 tablishment of this practice. 



Fumigation with best quality fresh 

 pyrethrum insect powder or dusting 

 the powder over the beds is also effec- 

 tive against the mushroom maggots if 

 taken in time, but tobacco fumigation 

 may be considered standard for this 

 use. 



THE MUSHROOM MITE 



The mushroom mite ^ (fig. 2) is a 

 minute, soft-bodied mite, smooth 

 skinned, and white or whitish in 

 color. It is closely allied to the com- 

 mon cheese mite ■* and resembles that 

 species in appearance. It is, if any- 

 thing, more prolific, becoming at 

 times so abundant in mushro<im beds 

 as to cover the surface of the com- 

 post ; when present in such numbers 

 it is extremely destructive, feeding 

 upon the mushrooms in all stages and 

 penetrating the bods and destroying 

 the mycelium. 5 Indee<i, in one case 

 observed, the mycelium was destroyed 

 as fast as it was produced. 



This species is undoubtedly the 

 cause in many cases of the failure 

 of the spawn to propagate, which is 

 likely to be attributed to poor or 

 weak spawn or to defective cultural 

 conditions. The minute size of the 

 mites causes their presence to be over- 

 looked and the failure of the spawn 

 to produce mycelium is not under- 

 stood. Even under conditions favor- 

 able to the growth of the mycelium 

 it is possible for the mites to in- 

 crease to such an extent that the en- 

 tire bed may be killed out. 



le propi 

 uidard 



•xtont that 

 no staiiciai'fl dose has as yet been formulated. 



^ T\irn(i};iphns Untnrri Osb. 



* Ttirnqhjphus siro I-. 



5 The term mycelinm. as used herein, is applied to the new prowth of spawn throuRh 

 the compost, as differentiated from the orisinal insertions of spawn. 



