Simulated Aerial Test on Western Spruce Budworm, 1981

Abstract

Abstract Fenitrothion was sprayed at two concentrations on 4th and 5th stage spruce budworm larvae on individual, small, Douglas-fir, in western Montana, 1 to 8 July. The concentrations were: 18 oz/gal and 9.15 oz/gal. Application was with a simulated aerial sprayer which was constructed to produce insecticide spray patterns which have the same characteristics as typical aircraft sprays. Forty-five trees were used in the test, 15 trees for each dosage and 15 controls. The mean volume of spray for each concentration was 2 m/per tree. This was calculated to be approximately equivalent to 0.4 gal/acre delivered to the ground. Percent mortality was calculated by assessing the difference in larvae per 100 buds between pretreatment and 10 days posttreatment. Pretreatment population densities were determined by sampling the larvae per 100 buds from randomly selected 15 in. branches from the midcrown of each tree just before spraying. Posttreatment population levels were assessed by again sampling 4 randomly selected 15 in. branches from the midcrown of the same tree 10 days after treatment. Four Kromekote spray cards were positioned next to each tree just prior to spraying, to determine both droplet size and droplet density.