Efficacy of Chlorantraniliprole Seed Treatments Against Armyworm (Mythimna unipuncta [Lepidoptera: Noctuidae]) Larvae on Corn (Zea mays).

Abstract

Mythimna unipuncta (Haworth) (Lepidoptera: Noctuidae) is an important insect pest of corn (Zea mays L.) in North America and can cause severe damage during outbreaks. Insecticides are the main control method; however, development of insecticide resistance poses management challenges and necessitates the use of novel insecticides. A synthetic insecticide, chlorantraniliprole, belonging to the anthranilic diamides, targets insect ryanodine receptors and is a potential alternative to conventional insecticides for management of M. unipuncta. We determined the efficacy of seed treatment with chlorantraniliprole alone compared with a positive control consisting of a neonicitinoid seed treatment of thiamethoxam and combinations of both compounds against M. unipuncta larvae in laboratory bioassays. Bioassays were conducted on two different growth stages of M. unipuncta larvae (instars 3 and 5) and two plant growth stages (V1 and V2 corn) in clip cages and whole plant experiments. Larval mortality, head capsule width, and feeding injury were measured. The chlorantraniliprole seed treatment alone or in combination with thimethoxam at different doses affected survival of M. unipuncta larvae. In all bioassays except one, larval mortality occurred earlier when a combination of chlorantraniliprole and thimethoxam seed treatment was used when compared with a thimethoxam alone seed treatment. Mythimna unipuncta larvae developed faster on the untreated control corn plants compared with corn with insecticide seed treatments. Foliar injury was low in both chlorantraniliprole alone and chlorantraniliprole + thimethoxam treatments compared with the control. Chlorantraniliprole thus offers potential alternative to conventionally used insecticides in the management of M. unipuncta in corn.