Stage-dependent predation by Euagoras plagiatus against Spodoptera frugiperda and Helicoverpa armigera larvae under laboratory conditions.

BACKGROUND: Spodoptera frugiperda and Helicoverpa armigera are destructive noctuid pests resistant to multiple pesticides. This study quantified predatory performance, functional response, searching efficiency, and prey preference across developmental stages of Euagoras plagiatus against second-instar larvae of both pests under laboratory conditions. RESULTS: All developmental stages of E. plagiatus successfully preyed on both species, with functional responses conforming to the Holling Type II model in most developmental stages. Maximum daily consumption increased significantly with predator development (S. frugiperda: F(5, 24) = 76.40, P < 0.01; H. armigera: F(5, 24) = 76.68, P < 0.01). Fifth-instar nymphs achieved the highest consumption of S. frugiperda (131.58 prey/day), while females consumed the most H. armigera (131.58 prey/day). Both stages also exhibited superior control efficiency (a/Th = 124.95 for nymphs against S. frugiperda; a/Th = 124.99 for females against H. armigera), indicating pronounced stage-dependent predatory capacity. Searching efficiency in fifth-instar nymphs and adults declined with increasing prey density, whereas preference assays revealed E. plagiatus preferentially attacked H. armigera when offered equal densities of both species. CONCLUSION: Fifth-instar nymphs and adults of E. plagiatus demonstrate substantial potential as biological control agents against second-instar noctuid larvae. © 2026 Society of Chemical Industry.