Shelf life assessment of EPN Heterorhabditis indica infective juveniles in different formulations under laoratory conditions

Entomopathogenic nematodes (EPNs), particularly Heterorhabditis indica, are gaining prominence as eco-friendly biological control agents against insect pests. However, the effective use of EPNs in field applications depends largely on their viability and survival during storage. This study was conducted to assess the shelf life of Heterorhabditis indica infective juveniles (IJs) suspended in various formulations under laboratory conditions over a 60-day period. The treatments included Calcium alginate (T₁), Aloe vera (T₂), Hydrogen peroxide (T₃), Polyvinyl propyl (T₄), Glycerol (T₅), Triton X-100 (T₆), and a water-based control (T₇). Survival of IJs was recorded at four intervals: 15, 30, 45, and 60 days after treatment (DAT). At 15 DAT, the highest IJ survival was observed in the Aloe vera (T₂) (44.67 IJs) and Glycerol (T₅) (45.33 IJs) formulations, followed closely by Hydrogen peroxide (T₃) and the control (T₇), indicating early-stage viability benefits. As the storage period progressed, a gradual decline in IJ survival was noted across all treatments. At 30 DAT, Glycerol (T₅) maintained the highest viability (42.33 IJs), followed by Aloe vera (41.00 IJs). This trend continued through 45 DAT, where Glycerol again demonstrated superior performance (38.67 IJs), suggesting its stabilizing effect on nematode longevity. At 60 DAT, Glycerol-treated suspensions retained the highest survival (35.33 IJs), significantly outperforming the control (24.00 IJs) and other formulations. In contrast, Polyvinyl propyl (T₄) and Triton X-100 (T₆) consistently showed the lowest survival rates across all time intervals. The results indicate that Glycerol and Aloe vera are promising substrates for enhancing IJ survival during storage, with potential to improve field efficacy and ease of commercial use.