Toxicity of selected insecticides to fall armyworms (Lepidoptera : Noctuidae) in laboratory bioassay studies

Efficacy of conventional and experimental insecticides against the fall arm yworm, Spodoptera frugiperda (J. E. Smith), was evaluated in laboratory bio assays. In a laboratory diet bioassay, third instars of a laboratory-strain were more susceptible to novel insecticides, including chlorfenapyr, metho xyfenozide, spinosad, and tebufenozide, than to a recommended insecticide, thiodicarb. In other laboratory bioassays, fall armyworms were fed field gr own cotton leaves, white flowers, or bells treated with one of two recommen ded insecticides, L-cyhalothrin or thiodicarb, or one of four experimental insecticides, chlorfenapyr, emamectin benzoate, methoxyfenozide, or spinosa d. First instar mortality was significantly greater on leaves treated with chlorfenapyr, L-cyhalothrin, or thiodicarb than for the untreated control a t 24 h after infestation (HAI). First instar mortality was significantly gr eater on leaves treated with all insecticides, with the exception of methox yfenozide, than for the untreated control at 48 HAI. Likewise, first instar mortality was significantly greater on white flowers treated with all inse cticides, with the exception of methoxyfenozide, than for the untreated con trol at 24 HAI. First instar mortality on white flowers treated with all in secticides was significantly greater than the untreated control at 48 HAI. Fifth instar mortality on bells was not significantly different among treat ments at 1 day after infestation (DAI). At 3 and 5 DAI, fifth instar mortal ity was significantly greater on bells treated with all insecticides, with the exception of methoxyfenozide and spinosad, than for the untreated contr ol. At 7 DAI, fifth instar mortality was significantly greater on bells tre ated with all insecticides, with the exception of spinosad, than for the un treated control. These data indicate that these recommended and experimenta l insecticides are effective in controlling early fall armyworm instars on cotton if larvae come in contact with these insecticides.