Leaf-cutter ants are major agricultural pests causing substantial crop losses. Biological control using entomopathogenic fungi offers an eco-friendly alternative to chemical methods. This study evaluated the pathogenicity of Beauveria bassiana (ISO77) against Atta laevigata (Hymenoptera: Formicidae) and determined lethal times (LT50 and LT99) under laboratory conditions. Ants were exposed to conidial suspensions at 1 × 10⁷ and 1 × 10⁸ conidia·mL⁻¹. Mortality was assessed at 25 ± 2 °C with a 12-hour photoperiod over 10 days. The fungus was pathogenic at both concentrations, with higher conidial levels accelerating mortality. PROBIT analysis indicated LT50 and LT99 values of 120 and 214 hours for 1 × 10⁷ conidia·mL⁻¹, and 93 and 157 hours for 1 × 10⁸ conidia·mL⁻¹, respectively. These results demonstrate the potential of B. bassiana ISO77 as a biological control agent for leaf-cutter ants
