Abstract

In this study, the pathogenicity of five Iranian isolates of Beauveria bassiana andMetarhizium anisopliae was evaluated against adults of Callosobruchus maculatus adults by immersion bioassay method at 27 ± 1°C and 60 ± 5% R.H. under laboratory conditions.Cumulative mortality of the cowpea weevil at day 11 after treatment with B. bassianaisolates IRAN 187C, IRAN 429C, IRAN 441C and M. anisopliae isolates IRAN 715C and DEM I001 by conidial suspensions at low and high concentration ranged between 29.4 to86.2, 9 to 88.3, 21.1 to 96.3, 24.8 to 84.4 and 20.9 to 80.9%, respectively. The LC₅₀ and LT₅₀ values for IRAN 187C, IRAN 429C, IRAN 441C, DEMI001 and IRAN 715C were 1.9×10⁷, 9.8×10⁶, 2.4×10⁷, 2.6×10⁸ and 1.2×10⁸ conidia/ml and 7.8, 6.7, 7.2, 7.7 and 7.8 day, respectively. IRAN 441C of B. bassiana had the highest virulence against adult cowpea weevil because it had lower LC₅₀ and LT₅₀ and caused the highest mortality (76%) in treatment by suspensions containing 1×10⁸ conidia/ml. B. bassiana had higher virulence than M. anisopliae against adult of cowpea weevil.

Key word: Biological control, immersion bioassay, virulence, cowpea weevil.