Insecticidal activity of Metarhizium anisopliae-mediated nanoparticles and fungal metabolites against the red palm weevil, Rhynchophorus ferrugineus

Abstract

This study evaluated the insecticidal activity of green-synthesized metallic nanoparticles (Ag, CuO, and ZnO) and the ethanolic extract of Metarhizium anisopliae against the red palm weevil ( Rhynchophorus ferrugineus ). Physicochemical characterization confirmed the successful synthesis and stability of the nanoparticles. Among the tested materials, AgNPs exhibited the greatest larvicidal activity (LC₅₀ = 568.0 ppm), outperforming both the fungal extract and the reference insecticide abamectin under the experimental conditions. GC–MS analysis of the M. anisopliae extract identified several bioactive metabolites, including 1,2,4-benzenetriol, oleic acid, and naphthalene derivatives. Enzymatic assays demonstrated that AgNPs markedly inhibited digestive enzymes, particularly amylase and protease, indicating disruption of nutrient metabolism. Gene expression analysis revealed treatment- and time-dependent modulation of inflammatory (IL6 and TNF) and detoxification (CYP450) genes. Molecular docking further suggested that fatty acid derivatives, particularly oleic acid, exhibited favorable binding affinities toward multiple insect protein targets, supporting their potential contribution to the observed insecticidal activity. Overall, these findings provide mechanistic insights into the insecticidal effects of green-synthesized metallic nanoparticles and M. anisopliae metabolites and support their potential as promising candidates for red palm weevil management. However, further field-based studies are required to validate their practical efficacy under natural conditions.