THE MYCOGONE DISEASE OF MUSHROOMS AXD ITS COXTROL. 9 



closed the fact that the disease is as prevalent in the beds of growers 

 who use imported spawn entirely as among those who use domestic 

 spawn. Instances of the use of both foreign and American manufac- 

 tured spawn hy growers in localities where the disease was present 

 have been noted in which there was no trace of the disease. It is 

 the general opinion among American growers that the disease was 

 introduced by imported spawn. 



In the course of the present investigations it has been possible to 

 propagate the parasite in the laboratory on pieces of blank spawn 

 bricks * in sterilized bottles. The mycelium of the fungus spreads 

 over the pieces of brick, eventually fruiting and producing spores of 

 Verticillium and Mycogone. These experiments prove that under 

 proper conditions the parasite will grow on the spawn bricks. The 

 growth of the fungus appeared to be superficial, and it could not be 

 ascertained whether or not the mycelium penetrated the bricks. No 

 reliable method has yet been evolved to determine the presence or 

 absence of the mycelium of Mycogone in spawn bricks. The ob- 

 servation of the writer has been that there are no marked differences 

 between spawn in an infected bed and that in healthy beds. 



Although our knowledge is incomplete as to the exact way in 

 which the parasite spreads through the beds, because of insufficient 

 experiments on this phase of the subject, it seems probable from the 

 limited data that the parasite does grow through the manure of the 

 mushroom beds and attacks the developing mushrooms, producing 

 spores by means of which the disease may be carried to other beds. 

 In addition to this method of reinfection, the question suggests itself 

 as to whether the fungus may not persist for long periods in the 

 lumber used in the construction of houses or beds. In order to deter- 

 mine this point many cultures were made from the wood secured 

 from diseased houses, but at the present time no definite conclusions 

 can be drawn. 



LONGEVITY OF THE FUNGUS. 



In order to obtain data which would be of assistance in devising a 

 method for the control of the mushroom disease, two distinct lines of 

 investigation on the subject of the longevity of the fungus were 

 inaugurated. Laboratory and field experiments were continued 

 during a period of over three years. While the experiments were 

 not sufficiently exhaustive to be conclusive, they are significant and 

 interesting. 



Laboratory experiments. — Many different sets of cultures were made 

 on corn meal in 1 OO-cubic-centimeter flasks. These were opened, 

 examined, and transferred at certain periods in order to ascertain 



1 Blank spawn bricks are bricks in which the mushroom mycelium has not been "run," or grown. 

 49597°— Bull. 127—14 2 



