2 CIRCULAR 45 7, U. S. DEPARTMENT OF AGRICULTURE 



Extensive experiments have demonstrated that the control of mush- 

 room insects and mites, after they have become established in the 

 houses x is very difficult, owing to the extreme sensitiveness of the 

 mushrooms to chemicals, and because the chemicals that have so far 

 been in use and are known to be safe to use do not readily penetrate 

 into the beds. Nevertheless, by means of sanitation, proper compost- 

 ing and heating, and fumigation, these pests can be reduced in num- 

 bers or entirely eliminated before the beds are spawned, and largely 

 prevented from entering the houses thereafter. 



This circular is designed to acquaint the grower with the principal 

 mite and insect pests of mushrooms, their life histories in a general 

 way, and the steps to be taken to prevent them from damaging the 

 crop. 



IMPORTANCE OF PROPER COMPOSTING FOR CONTROL 

 OF MUSHROOM PESTS 



Proper composting of manure for mushroom culture is an important 

 factor in the control of mushroom pests. Composting is best done on 

 a concrete floor. This prevents the entrance into the manure of many 

 pests from the ground, and if there is a gutter around the edge that 

 may be kept filled with water many fly maggots will be trapped and 

 drowned therein as they leave the manure. Whether the composting 

 is done on concrete or on the ground, the composting floor should be 

 well scraped and cleaned, drenched with a solution of 1 gallon of for- 

 maldehyde to 50 gallons of water, and allowed to air for from 2 to 4 

 days before the manure is placed on it. Some people are much more 

 sensitive to formaldehyde than others. Its use should not be at- 

 tempted by persons unfamiliar with its qualities without securing 

 expert advice. 



At the first turning the manure should be well forked over, all 

 lumps and cakes broken up, and straw added if necessary. The tem- 

 peratures within the heap, except at ground level, are too high to 

 allow insects and mites to survive, but both mites and insects can 

 develop in the cooler outside layer of from 3 to 6 inches. The heap 

 should therefore be kept well ricked up during the composting so 

 as to expose as little surface as possible to attack. Along the ground 

 level the temperatures are often under 100° F., oxygen is practically 

 lacking, and the carbon dioxide concentration is very high. Under 

 these conditions the manure may remain uncomposted until it is 

 turned and thrown to the outside of the heap. This combination of 

 low oxygen and high carbon dioxide concentration, while perhaps 

 causing pests to become inactive, probably kills very few of them and 

 does not prevent the entrance of others from the soil. It is impor- 

 tant, in turning compost heaps, that the layer at ground level and 

 that within 6 inches or so of the outside be thrown to the hottest 

 part of the heap, not only to kill any insect or mite pests that may be 

 present, but also to encourage more even and better composting. In 

 an average compost heap this hottest area begins about 1 or iy 2 feet 

 from the side and bottom, and ends about 6 or 7 feet from the side 

 and 6 to 10 inches from the top, as shown in figure 1. 



1 The general term "mushroom house,*' as used in this circular, refers to any location 

 where mushrooms are grown. 



