SOME MUSHROOM DISEASES AND THEIR CARRIERS 9 



tion of the growing crop is attempted, applications varying from 

 one-half ounce per 1,000 cubic feet upward to the limit mentioned 

 above should be tested, the minimum quantity required for a satis- 

 factory kill being used. 



Caution. — Fumigation with hydrocyanic-acid gas is a process re- 

 quiring considerable precaution in its application, as the gas is 

 extremely poisonous to human beings. It is therefore recommended 

 that Farmers' Bulletin 880 and Department Circular 380 2 be ob- 

 tained from the Department of Agriculture before undertaking this 

 method. If growing mushrooms are fumigated with hydrocyanic- 

 acid gas, they should receive a thorough airing over a period of some 

 hours before being marketed, as the retention of such gas as might 

 be absorbed by them or held in the gills during the process of fumi- 

 gation constitutes a possible source of danger to the consumer. 



INSECT POWDER 



Many large growers depend on the use of pyrethrum or Dalmatian 

 insect powder for the control of flies and springtails in mushroom 

 houses. This method is entirely safe and reasonably satisfactory, 

 and the insecticide may be used at a considerable strength without 

 possible injury to the crop. The powder may be dusted over the 

 beds or burned in the alleyways between them with equally good 

 results. A dosage of 1 pound per 1,000 cubic feet of space, applied 

 every other day during a period of two weeks, is the usual practice. 



Pyrethrum extracts are on the market and are also useful in con- 

 trolling insects. It is inadvisable, however, to use extracts prepared 

 with mineral oils or soap for spraying upon the beds, as a deleterious 

 deposit is thereby produced. 



Pyrethrum of the highest grade, composed of ground pyrethrum 

 flowers and packed in air-tight metal containers, should be used, as 

 the lower grades are likely to prove unsatisfactory. 



2 Sasscer, E. R., and Borden, A. D. fumigation of ornamental greenhouse plants 

 with hydrocyanc-acid gas. U. S. Dept. Agr. Farmers' Bui. 880, 20 p., illus. 1917. 

 Weigbl, C. A. calcium cyanide as a fumigant for ornamental greenhouse plants. 

 U. S. Dept. Agr. Circ. 380, 16 p., illus. 1926. 



