Use of reduced rate mixtures of organophosphate and pyrethroid insecticides for resistance management of tobacco budworm, Heliothis virescens (F.), in cotton

Abstract

Field and laboratory tests were conducted to determine the toxicity of profenofos/cyhalothrin mixtures to larvae of the tobacco budworm, Heliothis virescens (F.). In a field test, full, half, and quarter rate insecticide mixtures of profenofos and cyhalothrin were compared with full and half rates of each insecticide alone. Toxicity data were obtained with susceptible and pyrethroid-resistant first and third instar tobacco budworm larvae. Field data demonstrated that half rate mixtures of profenofos and cyhalothrin provided approximately equal control to full rates of each compound separately with susceptible larvae. With pyrethroid-resistant larvae, the half rate mix worked as well as the full rate of profenofos and much better than the full rate of cyhalothrin. Overall, the half rate mixture of each insecticide worked better on susceptible larvae than on resistant larvae. Cotoxicity values obtained from laboratory bioassays with each insecticide alone and in combination indicate that profenofos and cyhalothrin are acting independently in the mixture with first instars and antagonistically in the mixture with third instars. The data suggest that mixtures of profenofos and cyhalothrin at reduced rates will achieve control comparable to full rates of either insecticide alone. The data also suggest that reduced rate mixtures should be used before a resistance problem arises, not afterwards. That is, mixtures should be used to prevent resistance problems, not cure them.