Analysis of the virulence, infection process, and extracellular enzyme activities of against the Asian corn borer, guenée (Lepidoptera: Crambidae).

The control of , a major pest of maize in Xinjiang, is challenging owing to the occurrence of resistant individuals. Entomopathogenic fungi (EPF) are natural insect regulators used as substitutes for synthetic chemical insecticides. The fungus is highly pathogenic to ; however, its virulence characteristics have not been identified. This study aimed to analyse the lethal efficacy, mode of infection on the cuticle, and extracellular enzyme activity of against . We found that the mortality and mycosis of were dose-dependent when exposed to and varied at different life stages. The egg-hatching and adult emergence rates decreased with an increase in conidial suspension. The highest mortality (83.33%, 7 d post-infection [DPI]) and mycosis (74.33%, 7 DPI) and the lowest mortality response (8.52 × 10 conidia mL) and median lethal time (4.91 d) occurred in the 3 instar larvae of . Scanning electron microscopy indicated that numerous conidia germination and infection structure formation may have contributed to the high pathogenicity of against . There were significant correlations between mortality and the activities of extracellular protease, lipase, and chitinase of . This study revealed the infection process of the highly pathogenic against , providing a theoretical basis and reference for strain improvement and field application of EPF.