164 Diseases of Greenhouse Crops 



try from France with imported virgin spawn col- 

 lected at random from fields. The disease may be 

 introduced into a new place with the manure and 

 then spread quickly in a number of ways. Immedi- 

 ate precautionary measures are essential for the con- 

 trol of this trouble. Diseased plants when first no- 

 ticed should be pulled out and burnt. Allowing these 

 infected plants to decay in the beds is a sure means 

 of spreading the fungus broadcast. The gain from 

 keeping the beds free from diseased specimens will 

 more than compensate for the trouble. At the end 

 of the season the soil in beds should be carried away 

 to a distance where mushrooms will not be grown, al- 

 though it may be used for garden purposes, since 

 the Mycogone disease is known to attack only mush- 

 rooms. After the house has been thoroughly cleaned 

 out, it should be disinfected with the formaldehyde 

 gas method. This is carried out as follows: For 

 every thousand cubic feet of house space use three 

 pints of formaldehyde and twenty-three ounces of 

 potassium permanganate. The potassium perman- 

 ganate is placed in two or three earthen or wooden 

 vessels, each having a capacity of one quart to every 

 ounce of permanganate. When ready for the opera- 

 tion, the mushroom house is sprinkled with water, 

 the potassium permanganate placed in the recepta- 

 cles, the formaldehyde is poured evenly over the 

 permanganate, and the greenhouse doors are closed at 

 once. They are kept closed for twenty-four hours 

 and then opened to allow the formaldehyde fumes to 

 escape. All lights must be kept away from the house 



