Western Spruce Budworm Control with Orthene Implants,1978

Orthene medicaps were field tested near Cascade, Idaho, using a randomized block experiment. Each of the eight blocks contained four equal-sized Douglas-fir trees, 6 to 14 inches d.b.h., 25 feet tall. In each block treatment, medicaps (0.8 g ai) were implanted at the rate of I per 4,6, and 8 inches tree circumference. An untreated tree served as control. Implants were driven into a 1/2 inch hole, 2 inches deep, until the outer end was level with the cambium layer, then the hole in the bark was sealed. Implants were done on June 12, while buds were swelling, about I week before bud burst. Tallies of insect populations were based on counts from four midcrown branches at pretreatment and 3 posttreatment sampling intervals. Prespray populations were number of attack holes per 100 new buds; postspray populations were number of larvae per 100 new shoots. Defoliation was estimated as % of new needles eaten or destroyed at last sampling interval.