Variability in Foraging Behaviour, Thermal Requirement and Virulence of Entomopathogenic Nematodes against Sod Webworm, Herpetogramma phaeopteralis Guenee (Lepidoptera: Crambidae)

Variability in virulence among entomopathogenic nematodes, Heterorhabditis indica, H. bacteriophora and Steinernema abbasi, was studied for lethality, foraging behaviour in response to host volatiles, thermal requirements (degree-days), recyclability, persistence and field efficacy against Turfgrass Sod Webworm (TSW), Herpetogramma phaeopteralis. Comparatively, lethal concentration and time were lowest for H. indica against TSW. Recyclability of EPN ranged from 3.42 × 10⁵ to 4.23 × 10⁵ IJs g¹ of TSW. H. bacteriophora recorded highest movement rate on agar (0.38–0.78cm) and sand-agar (0.45–0.56cm), followed by S. abbasi, and H. indica. Responding to TSW volatiles, S. abbasi recorded maximum movement, H. bacteriophora, moderate, and H. indica, lowest. Heterorhabditis indica (with nictitation); S. abbasi and H. bacteriophora (without nictitation) were ambusher and cruiser, respectively. S. abbasi preferred warmer temperatures (30–33°C), H. bacteriophora, moderate (24–27°C), and H. indica, a wider range (24–30°C), for virulence based on thermal requirement. In field, EPNs were comparable to chlorpyriphos against TSW. We demonstrated the complementarity of thermal preferences of EPNs and insect pest was critical besides attributes like foraging behaviour, recyclability, persistence, and lethality values for their success in the field.