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Protecting Douglas-fir cones and foliage with a systemic insecticide Public Deposited
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Trees in a Douglas-fir stand infested with western spruce budworm were treated with a systemic insecticide to protect cone and seed production at three locations in Montana during 1983. Treatments applied were (1) acephate as an Acecap implant, (2) acephate as an Inject-A-Cide injection, and (3) control. Potential cone-bearing trees were selected and then randomly assigned one of the above treatments. Treatments were applied from mid- to late April. Cone buds varied from tight to recently burst. Data collected were as follows: tree heights and diameters, cone damage and infestation rate just after pollination, host tree defoliation from one location, estimate of external damage on mature cones, green cone weight, and seed per cone classified as full, hollow or damaged. Rates of infestation and damage on the small cones were not different by treatment. Foliage protection was between 56 and 74 percent. External cone damage and cone weights improved with both acephate treatments. Seed yield increased 69 to 82 percent for Acecaps and 65 to 84 percent for Inject-A-Cides. The proportion of full, hollow, and damaged seed did not change between treatments. In budworm-infested Douglas-fir, both Acecaps and Inject-A-Cides are an effective means to improve seed production.
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