Entomopathogenic Nematode Steinernema carpocapsae Venom Proteins Disrupt Developmental Physiology and Reproduction of Spodoptera frugiperda (Lepidoptera: Noctuidae).

The use of Steinernema carpocapsae infective juveniles as biological control agents is a long-standing practice, yet the oral impact of their secreted venom proteins on crop pests remains largely unknown. We evaluated the oral toxicity of S. carpocapsae venom proteins against Spodoptera frugiperda using artificial diet assays. Ingestion caused significant dose-dependent toxicity in early-instar larvae, resulting in mortality and a prolonged developmental duration. Carry-over effects were profound; treated pupae were smaller and malformed, with only 19% of larvae fed on 1000 ng g-1 venom protein-supplemented diet reaching adulthood compared to 92% in controls. Surviving adults lived 30% fewer days and laid over 90% fewer morphologically normal eggs. These physiological disruptions coincided with elevated oxidative stress and detoxification enzyme activity, suggesting the venom induces oxidative and detoxification responses, which may be associated with the observed phenotypic alterations. This study provides the first demonstration of the oral toxicity of entomopathogenic nematode venom proteins, positioning them as a promising resource for the discovery of novel insecticidal proteins for sustainable pest management.