Seed treatment with diamides provides protection against early and mid-stage larvae of the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), in maize

Abstract

The fall armyworm, Spodoptera frugiperda (J. E. Smith) is one of the major pests of maize worldwide. Farmers apply multiple rounds of pesticides within a single cropping season to control the fall armyworm. This leads to increased costs for plant protection and accelerates the selection pressure for evolution of resistance to various insecticide molecules in a short period. Hence, it is crucial to minimize the frequency of insecticide sprays on the crop. In this study we assessed the efficacy of seed treatment chemicals viz.- cyantraniliprole 19.8 % + thiamethoxam 19.8 % FS, chlorantraniliprole 62.5 % FS, and thiamethoxam 70 % WS against neonates and third instar larvae of S. frugiperda. Lab bioassays using leaves from seed treated plants were conducted. Results showed that thiamethoxam 70 % WS was completely ineffective. It was thus presumed that only cyantraniliprole contributed to the observed larval mortality in the combination chemical tested here. Although both cyantraniliprole and chlorantraniliprole were effective for up to a month, the latter consistently recorded greater larval mortality. As seed treatment is easy to practice, poses lower risk and economical, we recommend this application method, especially using chlorantraniliprole 62.5 % FS, as a part of the integrated pest management strategy to combat the fall armyworm in maize.