Evaluation of Metarhizium anisopliae Conidia on Different Solid Substrates and its Virulence Against Tobacco Caterpillar, Spodoptera litura (Fab.) (Lepidoptera: Noctuidae)

The efficacy of Metarhizium anisopliae spores against Spodoptera litura, a common pest in agricultural systems, was investigated through laboratory bioassays. The spore counts of M. anisopliae were analyzed across various locally available solid substrates (rice, sorghum, bajra, pigeon pea, wheat, ragi, and wheat germ), revealing significant variations. Wheat germ exhibited the highest spore count (11.23 x 107 spores/mL), while ragi showed the lowest (1.92 x 107 spores/mL). The mortality rates of S. litura larvae at different concentrations of M. anisopliae spores over 8 days were determined. Results indicated a concentration-dependent increase in mortality, with the highest concentration (1 x 108 spores/mL) resulting in 91.01% mortality by the 8th-day post-treatment. In addition, concentration-mortality and time-mortality responses were modeled, revealing an LC50 of 1.22 x 105 spores/mL and an LT50 of 5.19 days. These findings underscore the critical role of substrate selection in enhancing fungal efficacy, advocating for adopting biological control methods in pest management for long-term agricultural sustainability.. KEYWORDS :Biological control, Metarhizium anisopliae, Spodoptera litura, Spore toxicity, Substrate variation, Virulence