Western Spruce Budworm Aerial Field Tests, 1980

Two insecticides Bolstar 6EC (Sulprofos) and Imidan IE (Phosmet) were each applied at three dosage rates to 4th and 5th instar spruce budworm larvae in central Idaho, Jun 22-27, 1980. Both materials, except the 1.5 lb Imidan which was applied undiluted were mixed with water, with 0.1% rhodamine dye added as a marking agent. The chemicals were applied by helicopter at 45 mph and 50 ft above rreetops to 40-acre plots. Volume of spray applied was 1.5 gal/acre for imidan and 1.0 gal/acre for Bolstar. Five plots were treated at each dosage rate, with five additional plots for each chemical left as untreated checks. Populations were expressed as mean number of larvae/100 buds and sampled at mid-crown of 15 trees in each plot. Defoliation was assessed from the same sample trees at the 20-day post-treatment sampling period when 5 to 10 percent pupation had occurred. Test results may have been affected to an unknown degree by cool, rainy weather that prevailed for the duration of the test. Rain fell on all plots between 5 and 48 hours after treatment. Total rainfall during the 5 days of spraying was 0.74 inch.