Influence of Posttreatment Temperature on Toxicity of Pyrethroids to Five Species of Stored-product Insects

Toxicity, based on knockdown, was determined at two posttreatment temperatures for six pyrethroids. Posttreatment temperatures were 20 and 30°C. Pyrethroids tested were cyfluthrin, bioallethrin, flucythrinate, d -phenothrin, fenvalerate, and cypermethrin. All six pyrethroids were evaluated against adults of confused flour beetle, Tribolium confusum Jacquelin du Val. Two pyrethroids, cyfluthrin and bioallethrin, were evaluated on adults of lesser grain borer, Rhyzopertha dominica (F.), and larger grain borer, Prostephanus truncatus (Horn); and larvae of Indianmeal moth, Plodia interpunctella (Hubner), and almond moth, Cadra cautella (Walker). Beetles were exposed to insecticide-impregnated filter papers; moth larvae were treated topically. Cyfluthrin was associated with a negative temperature coefficient for T. confusum, P. truncatus, P. interpunctella , and C. cautella. Bioallethrin was associated with a negative temperature coefficient for R. dominica and P. interpunctella. However, d -phenothrin was associated with a positive temperature coefficient for T. confusum and was the least toxic of the pyrethroids. Our results suggest that field performance of the pyrethroids possessing negative temperature coefficients may be enhanced at cooler temperatures.