Steinernema carpocapsae as a promising biological control agent against Spodoptera frugiperda pupae

Entomopathogenic nematodes (EPNs), such as Steinernema carpocapsae, are recognised as effective biological control agents against various insect pests. The fall armyworm (Spodoptera frugiperda), a destructive lepidopteran pest, causes significant damage to crops and has developed resistance to chemical insecticides, highlighting the need for alternative control strategies. While much research has focused on other pests, limited studies have explored the interactions between S. carpocapsae and S. frugiperda pupae. This study aimed to evaluate the efficacy of S. carpocapsae against the pupal stage of S. frugiperda. Nematode preferences were tested across several experimental conditions, including comparisons between control and pupae, 1-, 5-, and 10-day-old pupae, female versus (vs.) male pupae, and uninfected vs. pupae infected for 24 or 48 h. The impact of light and dark conditions on nematode attraction was examined. Additionally, adult survival and oviposition were assessed in both infected and uninfected pupae. Results demonstrated a strong preference of S. carpocapsae for pupae over controls, with higher parasitism observed in 1-day-old pupae compared to older pupae and in pupae infected for 24 h compared to those infected for 48 h. No significant preference was observed between female and male pupae. Nematode survival was significantly higher in dark conditions compared to light conditions. Adults emerging from infected pupae exhibited significantly reduced survival and oviposition, with prolonged (48 h) exposure causing greater detriment than shorter (24 h) exposure. These findings highlight the potential of S. carpocapsae as a promising biological control agent against S. frugiperda, particularly during the pupal stage. This study provides valuable insights into the application of EPNs for sustainable pest management strategies in agricultural ecosystems.