An entomopathogenic strain of <i>Beauveria bassiana</i> (hypocreales: Cordycipitaceae) against <i>Eotetranychus kankitus</i> (acarina: Tetranychidae) and its compatibility with <i>Neoseiulus barkeri</i> (acarina: Phytoseiidae)

<i>Eotetranychus kankitus</i> is an important pest on several agricultural crops, and its resistance to pesticides has promoted the exploration of biological control strategies. <i>Beauveria bassiana</i> and <i>Neoseiulus barkeri</i> have been identified as potential agents for suppressing spider mites. This study aimed to investigate the pathogenicity of <i>B. bassiana</i> on <i>E. kankitus</i> and its compatibility with <i>N. barkeri</i>. Results showed that among the five tested strains of <i>B. bassiana</i>, Bb025 exhibited the highest level of pathogenicity on <i>E. kankitus</i>. Higher application rates (1 × 10⁸ conidia/mL) of Bb025 led to a higher mortality rate of <i>E. kankitus</i> (90.402%), but also resulted in a 15.036% mortality of <i>N. barkeri</i>. Furthermore, preference response tests indicated that both <i>E. kankitus</i> and <i>N. barkeri</i> actively avoided plants sprayed with Bb025 compared to the control group that was sprayed with Tween-80. In a no-choice test, we observed that <i>N. barkeri</i> actively attacked Bb025-treated <i>E. kankitus</i> with no adverse effect on its predatory capacities. Furthermore, <i>N. barkeri</i> laid more eggs when fed on Bb025-treated <i>E. kankitus</i> compared to Tween-80-treated <i>E. kankitus</i>, but the subsequent generation of surviving individuals fed on Bb025-treated <i>E. kankitus</i> was reduced. These findings demonstrate that the Bb025 strain of <i>B. bassiana</i> is highly virulent against <i>E. kankitus</i> while causing less harm to <i>N. barkeri</i>. Consequently, a promising strategy for controlling <i>E. kankitus</i> could involve the sequential utilisation of Bb025 and <i>N. barkeri</i> at appropriate intervals.