Abstract:  Beauveria bassiana (Balsamo) Vuillemin is one of the most important entomopathogenic fungi and has been widely used for many insect pests all over the world. In this study, the pathogenicity of nine isolates of B. bassiana was evaluated against adults of Tribolium castaneum (Herbst). Fifteen adults of the pest were submerged into the four suspensions (1×10⁶, 1×10⁷, 1×10⁸ and 1×10⁹ conidia/mL) of different isolates of B. bassiana for 20 s, and the mortality was recorded daily for 14 d. Results showed that IRAN 440C and IRAN 187C isolates had the lowest (5.04×10⁷ conidia/mL) and highest (5.05×10⁸ conidia/mL) LC₅₀, and DEBI 005 and DEBI 014 isolates had the shortest (2.88 d) and longest (4.96 d) LT₅₀, respectively. According to the LC₅₀ and LT₅₀ values and the mortality, IRAN 440C is a perfect isolate for using in controlling the pest.

Key words: Beauveria bassiana; Tribolium castaneum, pathogenicity, median lethal concentration (LC₅₀), median lethal time (LT₅₀)