Comparative assessment of biopesticides for the laboratory control of fall armyworm (Spodoptera frugiperda) (Lepidoptera: Noctuidae) in Benin

Abstract

The laboratory efficacy of three plant-based oil extracts (Ricinus communis, cashew nut shell liquid (CNSL), and Thevetia neriifolia), together with two positive controls (Topbio and the entomopathogenic fungus BotaniGard 22WP), was evaluated in this study for the management of S. frugiperda. Second and third instar larvae were exposed to increasing doses of each treatment, and larval mortality, feeding rate, weight gain, and mean observation time were recorded over a 14 day period. The experiment was arranged in a completely randomized block design with three replicates per treatment. A beta regression model was applied to analyze larval mortality in relation to treatment type and dose. Significant differences (p < 0.05) were observed among the tested biopesticides. Cashew nut shell liquid extracts resulted in the highest larval mortality from concentrations ≥2%, followed by Topbio and the entomopathogenic fungus BotaniGard 22WP, which also significantly reduced larval feeding and development. Extracts of R. communis and T. neriifolia exhibited moderate efficacy. Furthermore, Topbio and cold-extracted CNSL showed the lowest LD₅₀ values (0.0067984 and 0.0069042, respectively), indicating high toxicity against S. frugiperda larvae. Overall, the findings demonstrate the potential of biopesticides as effective alternatives to chemical insecticides and emphasize the need for optimization of their formulations and application strategies to enhance field-level performance. Keywords: fall armyworm; maize; biological control; biopesticides.