Effect of infectivity concentration for Mass Propagation of Heterorhabditis indica in Different Host

Entomopathogenic nematodes (EPNs) are promising biological control agents against several insect pests. This work assessed the effectiveness of three EPN inoculation techniques: spread plate, immersion and shaking on five insect hosts: Bombyx mori larvae (BML), Bombyx mori pupae (BMP), Galleria mellonella larvae (GML), Philosamia ricini larvae (PRL) and Philosamia ricini pupae (PRP). The spread plate method consistently resulted in the highest mortality, with BML exhibiting ~72% mortality followed by BMP (~64%), GML (~66%), PRL (~54%) and PRP (~44%). Mortality was significantly lower in the immersion and shaking methods (p < 0.0001). A dose-dependent response was observed with EPN concentrations ranging from 50 to 1000 IJs/mL where PRL showed the steepest increase in mortality (R² = 0.61) and PRP showed the lowest susceptibility (R² = 0.30). The emergence of infective juveniles also increased linearly with concentration, being highest in BML (R² = 0.90) and BMP (R² = 0.87) and lowest in PRP (R² = 0.94 but with lower absolute numbers). Control host GML maintained consistent mortality (~63–74%) and supported IJ emergence (~9–27), confirming its reliability as a baseline comparator. These findings highlight the influence of inoculation technique and host-specific susceptibility on EPN effectiveness, offering insights for optimizing biocontrol applications in integrated pest management programs.