Six pyrethroids, cyfluthrin, cypermethrin, deltamethrin, fenvalerate, flucythrinate and permethrin, and two organophosphorous insecticides, acephate and chlorpyrifos, were applied to the soil surface in the greenhouse and field to evaluate their effectiveness and residual toxicity against the darksided cutworm, Euxoa messoria (Harris), in Ontario.
Four years of tests indicated that the pyrethroid insecticides were consistently similar in effectiveness and residual toxicity at the rates applied. On air-dry soil surfaces in the greenhouse, the pyrethroids were significantly more toxic and persistent than was chlorpyrifos. On moderately moist soil surfaces in the field, chlorpyrifos was as toxic to the cutworm larvae as were the pyrethroid insecticides, but less persistent. None of the pyrethroids was affected by soil moisture to the same extent as was chlorpyrifos. Acephate-treated soil surfaces, regardless of indoor or outdoor conditions, were less toxic and the toxicity less persistent than with chlorpyrifos-treated soil. Although not statistically different, the high rates of pyrethroids were consistently more toxic and persistent to the cutworm larvae than the low rates of the same materials. All the pyrethroid insecticides have excellent potential as soil treatments for controlling cutworms on tobacco.