Relationship of Growth Reduction in Douglas-fir to Infection by Armillaria Root Disease in Southeastern British Columbia

Bloomberg, W. J., and Morrison, D. J. 1989. Relationship of growth reduction in Douglas-fir to infection by Armillaria root disease in southeastern British Columbia. Phytopathology 79:482-487. Stem volume growth during consecutive 5-yr periods was measured in were greatest for the past 5-yr period and least, though still significant, for four Douglas-fir (Pseudotsuga menziesii) stands infected by Armillaria the past 15-yr period. Trends during the past 30 yr showed greater declines ostoyae in the interior cedar-hemlock and montane spruce biogeoclimatic in severity classes 3 and 4 relative to class 0 than in classes 1 and 2. The zones of southeastern British Columbia. Growth, expressed as percent of period in which decline was initiated also occurred earlier (up to 25 yr ago) stem volume at the start of each period, decreased significantly as resinosis in classes 3 and 4 than in other classes. The percentage of basal increased due to mycelial colonization of the tree base. It was highest in circumference that was affected by lesion was strongly related to percent resinosis severity class 0 (healthy), lowest in classes 3 (> 50-100% of basal roots infected but only weakly to percent volume growth. The relation of circumference showing resinosis) and 4 (recently killed, 100% resinosis), percent basal circumference affected by lesion to percent volume growth and intermediate in classes 1 (no basal resinosis but root[s] infected within 1 was greatly strengthened by including the period in which decline was m of root collar) and 2 (<, 50% basal resinosis). Differences among classes initiated in the regression equation. Additional keywords: root rot.