Efficacy of Entomopathogenic Fungus Beauveria bassiana Isolates against Callosobruchus maculatus (Coleoptera: Chrysomelidae) under Controlled Conditions

Callosobruchus maculatus FaB (Coleoptera: Bruchidae), is a major field-to-store post-harvest pest of in the tropics and worldwide. They cause weight loss, decreased germination potential and reduction in commercial and aesthetic value as a result of physical contamination of grain by insects, eggs and excrement, decreased nutritional value. Entomopathogenic fungi have been employed in control of a number of storage pests and has been demonstrated to have potential in control of C. maculatus in cowpea during storage. Nine B. bassiana isolates were evaluated for effectiveness in controlling C. maculatus in cowpea grain under controlled laboratory conditions. Mortality of the bruchids was evaluated stepwise where the most effective isolate concentrations against C. maculatus were assessed. Initial assessment involved determination of the most effective concentration among the isolates following dilution. The isolates showed significant differences on the mortality of cowpea bruchids at the different concentrations. Isolate J35 had 98.2% mortality at 5 days after application during the first season and 88.3% during the second season, which was only lower to the formulated isolates BBC and BVT. The current study shows the pathogenic effectiveness of B bassiana on C. maculatus.