CONTACT AND FEEDING TOXICITIES OF ACEPHATE AND CARBARYL TO LARVAL STAGES OF THE WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALIS (LEPIDOPTERA: TORTRICIDAE)

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Abstract
Spray and feeding bioassays of acephate and carbaryl were conducted with each of the six instars of the western spruce budworm, Choristoneura occidentalis Freeman. Dose-mortality regressions were used to estimate overall relative susceptibility. Small differences in overall susceptibility of the six instars to acephate and large differences to carbaryl were observed. Application of carbaryl so that it would be present when second instars emerge from their hibernacula may maximize efficacy by minimizing the tolerance-instar effect. The efficacy of acephate may be relatively unaffected by instar-related changes in tolerance.