Toxicity of selected insecticides applied to western spruce budworm

Abstract

The contact toxicity of 100 insecticides to last stage larvae of Choristoneura occidentalis Freeman was tested by topical application in a 10-yr series of screening experiments. Pyrethroids were generally the most toxic group of chemicals tested. Compounds more toxic than the standard, mexacarbate, at Ld₅₀ were: bioethanomethrin, (+) cis-resmethrin, (+) trans-resmethrin, (+) cis-phenothrin. ENT 29117 (5-benzly-3-furylmethyl (IR,3S,E) 2,2-dimethyl-3- (2-oxo-3-tetrahydrothiophenylidenmethly) cyclopropanecarboxylate), resethrin, and NRDC 143 (3-phenoxybenzly(±) -3-(2,2-dichlorovinyl-2,2-dimethylcyclopropanecarboxylate). Mexacarbate spray was tested on the western spruce budworm at selected developmental stages. First instars were least susceptible at both LD₅₀ and ld₉₀; instars 3-5 and 6th instars weighing less than 110 mg were most susceptible. Since long-term laboratory rearing of insects did not change their responses to 3 representative chemicals periodically tested during this series of experiments, the results represented a valid estimate of relative toxicity.

Citation

Robertson, Jacqueline L., Gillette, Nancy L., Look, Melvin, Lucas, Barbara A., Lyon, Robert L. 1975. Toxicity of selected insecticides applied to western spruce budworm. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station. 6p.