Evaluation of indigenous Beauveria bassiana strains for biocontrol of Helicoverpa armigera

Abstract

This study aimed to isolate native strains of B. bassiana from insect cadavers and soil samples, assess their virulence against H. armigera larvae and evaluate their potential as biocontrol agents under laboratory conditions. Eight isolates (Bb-4, Bb-6, Bb-7, Bb-8, Bb-14, Bb-17, Bb-18, and Bb-20) along with standard culture Bb-1 were selected based on their growth and multiplication capacity. Conidial suspensions of these isolates were applied to third instar larvae at varying concentrations (1×10⁴ to 1×10⁸ spores/ml) and mortality was recorded over 10 days. The highest mortality (85%) was observed at the highest spore concentration (1×10⁸ spores/ml) for isolate Bb-6 followed by Bb-7 (80%) and Bb-1 and Bb-8 (75%). The study also calculated the median lethal concentration (LC50) and lethal concentration (LC90), with isolate Bb-6 exhibiting the lowest LC50 (3.59×10⁵ spores/ml) and LC90 (5.51×10⁸ spores/ml), indicating its superior pathogenicity. These results highlight the potential of B. bassiana as an effective biocontrol agent for integrated pest management programs targeting H. armigera, contributing to sustainable chickpea cultivation practices.