Abstract The destructiveness of Poria weirii Murr. as a root pathogen in coniferous forests is markedly increased through its longevity in wood buried in forest soil. Three experiments, with infected, 2-inch cubes of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, buried under a Douglas-fir stand, show that (1) the pathogen can survive as long as 5 years, even in small pieces of wood; (2) survival at depths of 12 and 24 inches is better than at 3 and 6 inches; (3) presence of zone lines is associated with longer survival; and (4) activity of soil micro-organisms most probably decreases survival.
E. E. Nelson (Wed,) studied this question.