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Laboratory Toxicity and Field Efficacy of Selected Insecticides Against Fall Armyword (Lepidopters: Noctuidae)

Hardke, Jarrod T., Temple, Josha H., Leonard, B. Rogers, Jackson, Ryan E.
Florida entomologist 2011 v.94 no.2 pp. 272
Sorghum bicolor, Spodoptera frugiperda, bioassays, dose response, field experimentation, grain sorghum, indoxacarb, insect control, insect pests, insecticide residues, lambda-cyhalothrin, larvae, lethal concentration 50, methoxyfenozide, mortality, novaluron, plant pests, residual effects, spinosad, toxicity
Fall armyworm, Spodoptera frugiperda (J. E. Smith), is an occasional but often serious pest of several southern row crops, including: cotton, field corn, and grain sorghum. The objective of these studies was to generate baseline dose-mortality responses for fall armyworm larvae in laboratory bioassays, to confirm field efficacy against natural infestations, and determine residual efficacy of selected insecticides. These studies evaluated four recently developed insecticides (chlorantraniliprole, cyantraniliprole, flubendiamide, and spinetoram) and five commercial standards (indoxacarb, lambda-cyhalothrin, methoxyfenozide, novaluron, and spinosad). In diet-incorporated assays, the LC50 values of chlorantranilprole and spinetoram were significantly lower than the LC50’s of all other insecticides. The results of a field trial against a native fall armyworm infestation in grain sorghum indicated that chlorantraniliprole reduced the number of infested whorls below that in the non-treated control and the lambda-cyhalothrin- and methoxyfenozide-treated plots at three days after treatment (DAT). At seven DAT, no insecticides significantly reduced the number of infested whorls below that in the non-treated plots. In residual efficacy studies, exposure of fall armyworm larvae to chlorantraniliprole- and cyantraniliprole-treated tissue resulted in significantly greater mortality compared to those exposed to non-treated tissue and lambda-cyhalothrin-, flubendiamide-, novaluron-, and methoxyfenozide-treated tissues at 7 DAT. In addition, chlorantraniliprole and cyantraniliprole were the only compounds which resulted in >40% mortality at 28 DAT. These results indicate that newer insecticides are equal to or more efficacious against fall armyworm than traditional insecticides.