Virulent Beauveria bassiana OR500626 strain effectively control Tetranychus urticae

The entomopathogenic fungus Beauveria bassiana OR500626 plays a pivotal role as a biological control agent for various agricultural pests, including the two-spotted red spider mite, Tetranychus urticae Koch. In the current study, we tested the ability of a promising strain of the fungus isolated from the tissues of the red palm weevil, Rhynchophorus ferrugineus in the eastern region of the Kingdom of Saudi Arabia. B. bassiana virulence was estimated based on LC₅₀ values calculated by Probit analysis of T. urticae, which were treated with a series of concentrations (1 × 10², 1 × 10⁴, 1 × 10⁶, and 1 × 10⁸ conidia/ml). The mortality percentages of immature stages were 15.98-100%, males 15.94%-100%, and females (28.92%-100%) with an estimated LC₅₀ value of 24.09×10³, 35.43×10³, and 11.03×10³ conidia/ml, respectively. Furthermore, electron microscopy confirmed the ability of B. bassiana to infect T. urticae. The results indicated that B. bassiana spores attached to the T. urticae spider body within about 12 hours. The germination of spores increased within 24-36 and penetrated the T. urticae cuticle after 96 hours of exposure.