Laboratory Evaluation of Native and Commercial Entomopathogenic Fungi Against Macrodactylus nigripes (Coleoptera: Melolonthidae) Associated with Maize Crops

Maize in Mexico suffers severe economic losses due to root-feeding and defoliating pests, among which Macrodactylus nigripes is particularly damaging, attacking roots during its larval stage and reducing pollination in adults. The intensive use of chemical insecticides has generated environmental impacts and resistance risks, driving the search for sustainable alternatives. In this study, the efficacy of entomopathogenic fungi (Beauveria bassiana and Metarhizium anisopliae), diatomaceous earth, and a chemical control was evaluated against larvae and adults of M. nigripes under laboratory (controlled) conditions. A completely randomized factorial design was employed, and mortality and survival were assessed using Abbott’s correction, Kaplan–Meier survival analysis, and Probit regression. Results revealed highly significant differences among treatments. The native strain of B. bassiana (MA-Bb1) achieved the highest Abbott-corrected cumulative mortality in L1 larvae (99.4 ± 1.0%) and adults (75.3 ± 3.9%), with lethal times (LT50) of approximately 1.1–1.3 days in larvae and 1.6 days in adults, outperforming commercial strains and diatomaceous earth. Chemical control exhibited immediate action (LT50 < 0.4 days). These findings highlight the potential of entomopathogenic fungi, particularly the native strain MA-Bb1 exhibited high pathogenicity against M. nigripes under laboratory conditions and represents a promising candidate for future biological control programs. Additional studies under semi-field and field conditions are required to confirm its effectiveness under agricultural production systems.