Beauveria bassiana: A promising biocontrol agent for Helicoverpa armigera

Abstract

Beauveria bassiana is a naturally occurring entomopathogenic fungus that infects and kills a wide range of insect pests. This study aimed to isolate and evaluate the pathogenicity of Beauveria bassiana against Helicoverpa armigera. B. bassiana was isolated from naturally infected insect cadavers collected from major field crop across various locations in Maharashtra. The cadavers were surface sterilized, and infected tissue bits were cultured on sabouraud dextrose yeast agar (SDAY) media. Out of 25 infected cadavers 16 samples showed positive growth of B. bassiana. Additionally, soil samples were collected from the rhizosphere of major crops, and B. bassiana was isolated using the Galleria bait and serial dilution methods. Out of 25 soil samples, 3 showed positive growth. The pathogenicity of twenty B. bassiana isolates was tested against third instar larvae of H. armigera. Larvae were treated with a spore suspension (1×10⁸ spore/ml) and incubated at 25±1 °C and 90% relative humidity. Observations recorded after 10 days indicated significant variability in larval mortality rates among the isolates. Nine isolates exhibited high virulence with mortality rates between 70% and 85%, with Bb-6 isolate showed highest efficacy 85% on 3rd instar larvae of H. armigera. These findings highlight the potential of specific B. bassiana isolates as biocontrol agents against H. armigera. Further field studies are recommended to validate their efficacy.