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Entomopathogenic Efficacy and Cuticle-degrading Enzyme Production in Beauvaria bassiana and Verticillium lecanii Isolates Targeting Adult Cowpea Weevils
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Emmanuel Olofu Ogbadoyi1
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Israel Kayode Olayemi2
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Hausatu Babayi3
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Dapo Oloruntade Olayinka1
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Authors Info & Affiliations
Abstract
Introduction
Cowpea weevils (Callosobruchus maculatus) are a major post-harvest pest responsible for significant quantitative and qualitative losses in stored cowpea across tropical regions. The growing concerns associated with synthetic insecticides, including environmental contamination, pest resistance, and human health risks, have intensified the search for sustainable biological alternatives. This study evaluated the efficacy of two entomopathogenic fungi, Beauveria bassiana and Verticillium lecanii, against adult cowpea weevils and examined the role of their cuticle-degrading enzymes in pest control.
Methods
Contact bioassays were conducted to assess adult weevil mortality and suppression of first-generation (F1) emergence following treatments with fungal isolates. Standard enzymatic assays were performed to determine the specific activities of protease, lipase, and exochitinase produced by the fungi isolates.
Results
Both fungi isolates induced progressive mortality in cowpea weevils, with B. bassiana demonstrating comparatively higher pesticidal activity. In addition, treatments with both fungi isolates significantly reduced F1 adult emergence, with emergence levels remaining below the 50% threshold considered indicative of effective population suppression. Enzymatic analysis showed that both fungi isolates produced measurable cuticle-degrading enzymes. V. lecanii exhibited relatively higher protease and lipase specific activities, whereas B. bassiana showed higher exochitinase activity.
Discussion
The observed pesticidal effects are attributable to the production of cuticle-degrading enzymes, which facilitate fungal penetration and infection of the pest host. Differences in enzyme activity between the isolates may explain variations in their pathogenicity.
Conclusion
Beauveria bassiana and Verticillium lecanii showed potential as environmentally sustainable biocontrol agents for managing cowpea weevil infestations in stored cowpea.
