Spodoptera frugiperda susceptibility to novel and standard insecticides

The fall armyworm remains one of the most common and important migratory pests in many U.S. cropping systems. Traditional IPM practices rely heavily on chemical control strategies to manage this pest. Therefore, the objective of this experiment was to evaluate Spodoptera frugiperda (J. E. Smith) susceptibility to selected insecticides. All tests were performed on larvae (L3 stage, 30-45 mg) of a laboratory colony originating from collections in cotton and corn. The colony was validated as the corn strain of S. frugiperda using mitochondrial markers. Eight Insecticides were evaluated against S. frugiperda including four novel insecticides: chlorantraniliprole, cyantraniliprole, flubendiamide, and spinetoram; and four common commercial standards: novaluron, methoxyfenozide, and spinosad, and lambda-cyhalothrin. Serial dilutions were developed from formulated insecticides and then incorporated into meridic diet and diluted with water to develop selected doses for all bioassays. Larval mortality was measured at 96 HAT. Insects were classified as dead if they were unable to right themselves after being placed on their dorsal surface. Dose-mortality responses were summarized and LC₅₀’s used to compare toxicity among compounds. A wide range of LC₅₀ values were detected for third instars and ranged from 0.066 µg/ml (spinetoram) to 5.27 µg/ml (lambda-cyhalothrin). Lower LC₅₀ values (0.066 µg/ml to 0.93 µg/ml) generally were observed among the novel insecticides when compared to that for the traditional products (0.166 µg/ml to 5.27 µg/ml). All compounds were significantly more toxic than lambda-cyhalothrin using this protocol.