Management implications of western gall rust in precommercially thinned lodgepole pine stands

Twenty-four lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) stands, 26-32 years of age, which had been thinned at 15-23 years of age, were examined in west-central Alberta. Stand age at thinning was the single best predictor of subsequent gall formation on trees that were gall free at thinning (post-thinning infection). Stand height at thinning also was a good predictor of post-thinning infection, following adjustment for the effects of stand location and years of heavy infection. Gall incidence per tree at thinning was the best predictor of stem gall incidence on all trees, including those that had stem galls at the time of thinning (total infection). Stem infections declined with tree age and height. Nearly 60% of the stem galls encircled 40% or less of the stem. There was no relationship between degree of encirclement and either gall height or gall age. In locations where gall rust is common, managers should consider delayed thinning.