Pest Damage Incidence in Natural and Thinned Lodgepole Pine in Alberta

Thinned stands of young lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in west-central Alberta had a higher incidence of attack by common pest organisms than unthinned stands. Based on a sample of nearly 3000 potential crop trees (on 240 temporary plots) growing on 120 naturally regenerated cut blocks, the rate of attack in thinned vs. unthinned stands was 30% and 18% for western gall rust (Endo-cronartium harknessii (J.P. Moore) Y. Hiratsuka) and 25%. and 16% for leader damage due to terminal weevil (Pissodes terminalis Hopp.) and pitch twig moth (Petrova spp.) Damage from other agents, including that from small mammals, was low and little affected by thinning. Forest management implication of these results are discussed. Key words: western gall rust terminal weevil, pitch twig moth, snowshoe hares, red squirrels.