38 



It attacks the fruit bodies in all stages, thereby making these 

 unsightly and unsalable. When present in large numbers it actually 

 eats big holes right through them. It not only attacks the fruit bodies, 

 but even feeds on the mycelium underground, thus destroying the plant 

 entirely. 



Many cases where beds have not jdelded at all, and where the blame 

 has been credited to "old and dead" spawn, are doubtless truly the 

 results of this pest, which being so small has escaped notice. 



In two or three cases where the failure of a bed was attriljuted to 

 poor spawn, it was found on investigation that the "brick" had been 

 all right and had begun sending out mj^celium under favorable condi- 

 tions, but that myriads of these mites in the ground actually consumed 

 it as fast as it grew. In some beds they were so numerous that they 

 covered the surface entirely, and any such bed might as well be given 

 up at once, and the danger to surrounding beds somewhat minimized 

 by the killing of all the mites. This may be done by pouring boiling 

 water on the bed, using enough to reach the bottom and soak the bed 

 thoroughly. 



The following remedies were thoroughly experimented with and 

 none proved of much value: 



(A) Bisidphid of carhoQi. — Some twenty-odd beds, 3 by 6 feet, and 

 two beds, 5 by 10 feet, were under observation in two different places. 

 These beds were originally prepared with these experiments in view, 

 and the boxes were made li to 2 inches higher than is usually necessary, 

 so as to leave that much space above the ground. In other respects 

 the beds were prepared in the usual manner, the spawn was put in, 

 and in due time mycelium developed and mushrooms appeared. 



As soon as the mites put in their appearance (they were probably 

 brought in the adolescent stage with the manure) the bisulphid of 

 carbon was applied. From one-fourth of a pound to 1 pound was 

 poured into each of three or four shallow receptacles placed on top of 

 the bed, and the whole was then tightly covered with heavy oilcloth. 



This was done in the evening and the bed left overnight till the 

 next noon, when the soil was examined. 



It is possible that some of the mites had perished from the effect of 

 the poison. Several were found dead or djdng, but many more speci- 

 mens crawled upon and in the soil as lively as ever and apparently not 

 the least harmed. 



The treatment was repeated next night on some of the beds, and for 

 several nights on other beds, but with the same very doubtful success. 



A number of living mites were placed in a vial on a bit of mush- 

 room and the vial closed with cotton saturated with l)isulphid of car- 

 bon. After two days several mites were still alive, and the cause of 

 the death of the others may as well have been lack of moisture or 

 injury in handling them as the bisulphid of carbon, 

 8258— No. 38— 02— —3 



