Pathogenicity of the entomopathogenic fungi Beauveria bassiana(Balsamo)Vuillmin,Beauveria brongniartii Saccardo and Metarhizium anisopliae Metsch to adult Oryctes elegans Prell and effects on feeding

ABSTRACT: The Pathogenicity of entomopathogenic fungi Beauveria bassiana, Beauveria brongniartii and Metarhizium anisopliae (Ascomycota: Hypocreales) to adult Oryctes elegans (Coleoptera: Scarabeiidae) was tested in the laboratory. All the isolates tested were pathogenic to O. elegans. Five concentrations (108, 5.0× 108, 109, 5.0×109and 1010 conidia mL-1) of three fungal species were used for dose–response mortality [lethal concentration to 50% mortality (LC50) and lethal time to 50% mortality (LT50)]. M. anisopliae isolate DEMID 01 had the lowest LC50 value of 5.69 × 108 conidia mL-1 and B. bassiana had the highest LC50 value of 1.53 × 109 conidia mL-1. The LT50 values ranged from 6.05 to 10.89 days with M. anisopliae concentrations, from 6.45 to 10.12 days with B. brongniartii concentrations and from 7.21 to 11.62 days with B. bassiana concentrations. The effect of fungal infection on feeding, fecundity and egg viability of O. elegans adult females was also investigated under laboratory conditions. B. bassiana, B. brongniartii and M. anisopliae isolate were tested for feeding experiment using six concentrations (0, 104, 5.0× 104, 105, 5.0×105and 106 conidia mL-1). For reproduction potential (fecundity and egg viability) bioassays, six concentrations (0, 104, 5.0× 104, 105, 5.0×105and 106 conidia mL-1) of B. bassiana, B. brongniartii and M. anisopliae were used. Adult Bunch stalk borer (BSB) treated with M. anisopliae, B. brongniartii and B. bassiana treatments at all the concentrations consumed significantly less food than beetles in the control 14 days post treatment. Female beetles in the control treatments laid more eggs than fungus treated females. There was significant differences between controls and fungus 14 days post treatment. Results showed that M. anisopliae are pathogenic to BSB and infection can reduce feeding and fecundity.