Comparative efficacy of Heterorhabditis bacteriophora, Photorhabdus luminescens and Beauveria bassiana against different developmental stages of Bactrocera cucurbitae.

Tephritid fruit flies are among the most destructive insect pests of horticultural crops worldwide and can cause severe yield losses in cucurbit vegetables. The present study evaluated the efficacy of three entomopathogens, Heterorhabditis bacteriophora (Poinar), Photorhabdus luminescens (Thomas and Poinar), and Beauveria bassiana (Balsamo), against the different developmental stages of Bactrocera cucurbitae under laboratory conditions. Bioassays were conducted against maggots (3rd instars), pupae, and adults using different concentrations of each entomopathogens. Significant mortality was recorded in maggots and pupae, whereas no mortality was recorded in adults. Among all these entomopathogens, P. luminescens (1×109 CFU/mL) was highly effective against fruit fly larvae and caused 100% mortality after 120 h of exposure. Similarly, B. bassiana (1×109 conidia/mL) was most effective against fruit fly pupae, followed by H. bacteriophora (100IJs/mL). Probit analysis revealed stage-dependent susceptibility, with lower LC₅₀ values observed for maggots than pupae. The LC₅₀ values for maggots were 20.4 IJs/mL for H. bacteriophora, 3.2 × 105 CFU/mL for P. luminescens, and 4.6 × 105 conidia/mL for B. bassiana. In pupae, the LC50 values were 66.8 IJs/mL for H. bacteriophora and 7.1 × 105 conidia/mL for B. bassiana. The findings demonstrate the potential of entomopathogens as environmentally safe alternative for managing immature stages of B. cucurbitae. Further studies should focus on field validation and formulation development to enhance their practical applicability in integrated pest management programs.