MUSHROOM GROWING IN THE UNITED STATES 



19 



room manure or that may be contaminated by cattle, horses, drain 

 water, etc., from such fields. These precautions are especially 

 necessary in congested centers of mushroom growing. If there is 

 any doubt about the presence of the fungus in the soil it should be 

 used on small test beds before risking its use on a large scale. When 

 no Mycogone-free soil is available the fungus may be eradicated from 

 the soil by heat treatment as described later in the discussion of 



Figure 11. — The effect of temperature on the rate of growth of mushroom mycelium 

 in compost. The numbers at the top of the test tubes refer to the incubation 

 temperatures in degrees Fahrenheit 



mushroom diseases. In a disease-infested area care must be taken 

 from the digging of the soil to the screening and placing on the beds 

 to prevent the soil from coming into contact with contaminated tools. 



GROWING CONDITIONS 



TEMPERATURE 



The temperature at which the house is held largely determines 

 the length of the growing period and has considerable influence on the 

 quality of the mushrooms. If the temperature is kept between 45° 

 and 55° F. good beds continue to bear mushrooms for five or six 

 months, whereas in a house held at 60° to 65° the beds exhaust 

 themselves in three months. In the former case, as a rule, the 

 mushrooms grow somewhat larger and are distinctly firmer and 

 heavier than those grown at the higher temperatures. The total 

 yield is approximately the same with perhaps a slight advantage 

 in favor of the beds held within the low temperature range. When 

 two or more crops are grown in one season, time is an important 



