Laminated Root Rot: New Considerations For Surveys

In 1981, Douglas-fir (Pseudotsuga menziesii) trees were placed into 3 disease classes of 45 trees each based on signs and symptoms of Phellinus weirii infection: infected, probably infected, and probably not infected. Trees that died during the course of the study were felled and their stumps and roots removed from the soil, cleaned carefully, dissected, and examined. In August 1991, the remaining study trees were similarly treated. Eight trees recorded as infected in 1981, based on the presence of ectotrophic mycelium, were found to be not infected in 1991. Only one-third of the trees near inoculum sources, and thus expected to be infected, were infected. Of the trees thought to be not infected, one-third were infected. Based on limited observations, laminated root rot appears to be distributed both as "pockets" (aggregated) that appear as openings early in stand development and in a more "diffuse" manner that may lead to openings late in stand development. These findings have implications for disease survey and disease management. West. J. Appl. For. 12(2):49-51.