Effect of Incorporation on the Efficacy of Selected Pyrethroids for Control of Black Cutworm (Lepidoptera: Noctuidae)

Laboratory-reared black cutworm, Agrotis ipsilon (Hufnagel), larvae were used to determine if incorporating fenvalerate and permethrin in the soil to a depth of 8 cm would alter efficacy. Laboratory bioassays were done 0, 7, 14, and 21 d after application. Results of second- and fourth-instar bioassays show that second instars are more sensitive to fenvalerate and permethrin but require 89% more handling time than fourth instars. Incorporation significantly reduced the efficacy of fenvalerate and permethrin. Decreased efficacy from incorporating permethrin was counteracted by increasing the application rate from 0.113 kg(AI)/ha to 0.226 kg(AI)/ha, the maximum labeled rate. Incorporation of fenvalerate reduced efficacy to an unacceptable level even at the maximum labeled rate. Limited data suggest that incorporation also affects cyfluthrin and esfenvalerate adversely.