008 - JOURNAL OF FORESTRY 



unmerchantable portions of cut, diseased trees, and all other infected 

 slash on sale areas. 



In starting out to show the need of forest sanitation a brief discussion 

 of the principal factors concerned in the infection of trees by various 

 disease-producing agencies is necessary. 



Wood-rotting fungi are capable of producing sporophores following 

 the death of the host, and in such cases as Trametes pint there are often 

 more sporophores produced on the fallen host in most forest types of 

 the Northwest than at the time the host was alive. These factors are 

 important from the viewpoint of leaving infected slash and infected 

 snags and live trees on cut-over areas where they may develop in- 

 numerable fruit bodies and by the liberation of large masses of spores 

 threaten the health of susceptible trees. It has been determined by 

 Buller^ from partial counts that an average of 1,700,000 spores were 

 produced from each pore on the lower surface oi Polyporus squaniosus, 

 or a total of more than eleven billion for the entire lower surface, 

 which had an area of 38.75 square inches. He also states that a sporo- 

 phore of the same fungus kept under observation continuously gave off 

 clouds of spores during a period of 13 days. A million spores a 

 minute for two or more days were recorded. These spore clouds may 

 be observed under certain conditions in the forest. Buller further 

 states that the number of spores produced by a single specimen of this 

 fungus may in the course of a year be some fifty times the population 

 of the globe. This gives some idea of the enormous number of spores 

 set free from sporophores developing upon infected trees and infected 

 slash found on cut-over areas. Although no counts have been made of 

 the spore production of some of the most harmful Polypores, yet there 

 is no reason to believe that they will fall much below the figures given 

 above. The sporophores of Trametes piiii, Polyporus schweinitsii, and 

 Bchinodontium tinctorium produce spores over a considerable period of 

 time during the favorable part of the season. In the case of certain 

 fungi which sporulate during the early part of the season, spore pro- 

 duction is renewed again during the fall rainy season. Some of our 

 most destructive tree fungi show extreme hardiness to low tempera- 

 tures and will grow and produce spores during winter weather, and 

 abundantly with the first return of favorable conditions. The enor- 

 mous number of spores produced depend principally upon air currents 

 for their distribution to susceptible host trees. In this connection an 

 open stand lends itself to a greater distribution of the spores than a 

 closed one. A dense stand through which horizontal air currents are 



