16 MANUAL OF TREE DISEASES 



The trees may be enveloped for only an inch or two above 

 the soil with no considerable damage resulting, while at other 

 times the entire plants or such a large part of their leaf- 

 surface is covered that the trees die. The projecting shelves 

 and the incrusting layers developed over the trees are the 

 fruiting-structures of the fungus. The under and outer sur- 

 face of the fungous layers is smooth and covered with branches 

 of the mycelium which form spores at their tips. These spores 

 are snapped off when mature and are distributed by the wind. 

 In the seed-bed, however, the mycelium grows rapidly through 

 the soil and thus distributes the fungus over large areas without 

 the necessity of spore dissemination. 



When injury from the smothering fungus occurs, it is advis- 

 able to remove the affected plants and those just adjacent, by 

 lifting the soil containing them with a spade. Merely pulling 

 the trees will leave the vegetative portion of the fungus in the 

 soil where it can continue to spread. When the affected 

 plants are removed, measures should also be taken to reduce 

 the soil and atmospheric moisture in the beds, by draining off 

 excessive soil-water and removing any structures which shade 

 the beds. These measures must be limited, however, so as 

 not to predispose the plants to sun-scorch (see page 9). Thin- 

 ning the seedlings may be advisable under conditions in which 

 the moisture factor cannot be otherwise easily controlled. 



References 



Hartig, R. Pseudo-parasites. In Text-book of the diseases of trees, 

 pp. 35-36, fig. 8. 1894. 



Freeman, E. M. The smothering fungus of seedlings. In Minne- 

 sota plant diseases, pp. 243-244. 1905. 



