Growth characteristics of Phellinus (Poria) weirii in soil and on root and other surfaces
Growth of Phellinus (Poria) weirii (Murr.) Gilbertson from alder block inoculum into the surrounding soil to infect healthy roots was less than 10 cm. Tree-to-tree spread of this root rot fungus, beyond that which would occur as a result of root contact, may be facilitated by growth of the mycelium over roots of minor vegetation and over wood buried in soil. Ectotrophic mycelium is profuse on the bark of infected roots of Douglas fir (Pseudotsugamenziesii (Mirb.) Franco) and western hemlock (Tsugaheterophylla (Raf.) Sarg.), limited on infected roots of pine (Pinusmonticola Dougl., P. contorta Dougl, P. ponderosa Laws.), and nearly absent on infected roots of western red cedar (Thujaplicata Donn). Rate of spread of P. weirii root rot through stands with a high component of western red cedar or pine, or both, should be considerably slower than in pure stands of Douglas fir.