BULLETIN 127, U. S. DEPABTMEXT OF AGEICULTUEE. 



THE DISEASE IN MUSHROOM BEDS. 



The study of the mushroom disease in America has proved the 

 fungus to be exceedingly variable as regards the time of its appear- 

 ance. In some instances evidences of Mycogone were observed when 

 the mushrooms were just beginning to appear; again, the crop was 

 well developed before being attacked b\ r the parasite. The experience 

 of the French growers also proves that the time of the appearance of 

 the disease is subject to great variation, but that ordinarily it reaches 

 its height about the middle of the productive period of the beds. 



The occurrence of diseased mush- 

 rooms in an infected house is very 

 sporadic. Sometimes isolated dis- 

 eased specimens will appear among 

 normal mushrooms, while again per- 

 fectly healthy mushrooms will be 

 observed growing in a badly dis- 

 eased bed. An example of a badly 

 diseased specimen growing among 

 normal mushrooms is illustrated by 

 figure 1. 



PROPAGATION AND DISSEMINATION OF THE 

 DISEASE. 



The manner in which the parasite 

 is propagated in the beds is only 

 partially known, but from the ex- 

 perience of foreign growers and the 

 studies of the writer there can be 

 little doubt that the disease is dis- 

 tributed by the spawn and that the 

 fungus grows up with the mycelium 

 of the mushroom, which it finally 

 attacks and destroys. 



A thorough investigation of one 

 of the American mushroom spawn- 

 manufacturing plants in which the 

 so-called "tissue method" of spawn making is practiced leads to the 

 conclusion that there is little chance of the disease being carried by 

 the spawn where proper precautions are taken to prevent infection. 

 To prevent infection of the spawn entails great care on the part of 

 the manufacturer. He must be absolutely sure that his cultures are 

 made under sterile conditions and that the bricks are kept from any 



Investigation and 



Fig. 2. — Mycogons spores, showing the thick- 

 walled and warty cells. Magnified 425 

 diameters. From a photomicrograph by 

 Dr. Albert Mann. 



chance of contamination b}^ spores of the parasite, 

 inquiry among most of the large growers in this 



country have dis- 



