Symptom Expression of Root-Diseased Trees in Mixed Conifer Stands in Central Washington

Abstract Two proposed seed-orchard sites on the Wenatchee and Gifford Pinchot National Forests were examined prior to tree felling and land clearing to evaluate root-disease symptom expression in three species of conifers (Douglas-fir [Pseudotsuga menziesii], grand fir [Abies grandis], and ponderosa pine [Pinus ponderosa]. About half of the trees within infected areas had roots decayed by one of three principal root pathogens, Armillaria ostoyae, Phellinus weirii, and Fomes annosus, as determined from totally excavated root systems. Trees with above-ground symptoms had significantly moreroot decay than trees without symptoms. Crown symptoms and root-collar symptoms were accurate indicators of 22% of the root-diseased trees. Stain or decay at freshly cut stump surfaces were reliable indicators of 50% of root-diseased trees. Surveys that record crown symptoms and root-collar symptoms in similar stands will give accurate estimates of the number of trees killed by root diseases. However, examination of freshly cut stump surfaces will detect more accurately the total number of root diseased trees, especially if decay associated with butt wounds is absent. West. J. Appl. For. 1:46-48, April 1986