Toxicological Studies on Cutworms. I. Laboratory Studies on the Toxicity of Insecticides to the Dark-Sided Cutworm1

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Abstract
Laboratory tests indicated that several insecticides were more toxic than DDT as direct contact poisons to larvae of the dark sided cutworm, Euxoa messoria (Harris). The larval instars showed a marked difference in tolerance to DDT and Dursban® (O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate), and became increasingly tolerant with each successive instar. Tests with emulsifyable concentrates applied to the soil surface indicated that Dursban and Bayer 37289 (O-ethyl 0-2,4,5-trichlorophenyl ethylphosphonothioate) were effective at 1-2 lb per acre, parathion and DDT only at 4 lb per acre. Soil moisture influenced the toxicity of the emulsifiable concentrates, as did method of application. The use of a surfactant did not significantly increase the toxicity of either DDT or Dursban on the soil surface. Tests with various types of formulations applied to the soil surface indicated that dusts were the most effective; emulsifiable concentrates and wettable powders are equally effective and better than granules. Stomach poisons were more effective than contact poisons. Bran baits treated with DDT or Dursban were more effective at low concentrations. However, toxicity did not increase with increasing concentration and, at higher concentrations, soil treatments were more effective. Rye treated with emulsifiable concentrates of DDT or Dursban proved to be a highly attractive bait, and the insecticides were from 4-8 times as toxic as soil treatments. The results suggested that several insecticides, which would not be effective as soil treatments, would provide highly effective cutworm control if attractive forms of bait could be developed.