Toxicological Studies on Cutworms. VI. Laboratory Studies on the Toxicity of Several Experimental Insecticides to the Dark-Sided Cut worm as Soil Treatments and Stomach Poisons12

Abstract

Laboratory tests indicated that larvae of Euxoa messoria (Harris) were highly tolerant to aldrin and chlordane both as soil and rye foliage applications. The toxicity of 3 experimental materials, phoxim, chlorphoxim, and Stauffer N-2596 ( S -( p -chlorophenyl) O -ethyl ethylphosphonodithioate), to 4th- and 5th-instar cutworms was compared with results obtained with 3 standard insecticides, Bay 37289 ( O -ethyl O -2,4,5-trichlorophenyl ethylphosphonothioate), DDT, and Dursban® ( O, O -diethyl O -3,5,6-trichloro-2-pyridyl phosphorothioate). In addition to Bay 37289 and Dursban, N-2596 and phoxim showed potential as soil insecticides to replace DDT. Soil moisture had a pronounced influence on the toxicity of all the insecticides. As rye foliage treatments, the 3 experimental materials were also effective, with phoxim being equivalent in toxicity to Dursban, and N-2596 and chlorphoxim to Bay 37289. All were more effective than DDT. DDT was highly persistent on the rye crop, but the persistence of biological activity of the 5 oreganophosphorus insecticides, particularly phoxim, was very short. While it appears that these materials will be effective against cutworm larvae, accurate timing of spray schedules to coincide with cutworm hatch and favorable climatic conditions for insecticide activity will be essential.