Western Spruce Budworm Aerial Field Test, 1979

Three insecticides, Pounce, Imidan, and Sevin 4-oil, were each applied at 3 dosage rates against 4th and 5th instar larvae of the western spruce budworm in central Montana, July 3-10. Pounce and Imidan were each mixed with water for a total applied volume of 1 gai/acre with 0.1% rhodamine dye added as a marking agent. The chemicals were applied with 8002-flat fan nozzle tips from a helicopter 50 ft above treetops at 45 mph. Spray plots were 50 acres in size and at 5500-6000 ft elevation. Five plots were treated at each dosage rate, with 5 additional plots for each chemical left untreated as checks. Larval populations from 15 Douglas-fir trees in each plot were measured before spray and at 3 intervals after spray. Defoliation was assessed from the same sample trees when more than 50% pupation had occurred. Although Sevin 4-oil (carbaryl) currently is registered at 1 lb ai/acre for control of the western spruce budworm, tests of lower dosage rates were conducted. Procedures and design were the same as for the 2 new chemicals, except the Sevin 4-oil was mixed in diesel fuel and applied at a total volume of 0.5 gal/acre by Beecomist nozzles.