Isolation and characterization of an entomopathogenic fungus for Nilaparvata lugens control and its effects on host-associated bacterial community.

The brown planthopper, Nilaparvata lugens, is a major rice pest causing significant yield losses across Asia. Concerns over the environmental, health, and resistance-related impacts of current chemical control strategies highlight the need for sustainable alternatives. In this study, we isolated and characterized a novel entomopathogenic fungus, strain NLS-1, from mycosed N. lugens cadavers. Based on morphological observations and internal transcribed spacer (ITS) sequence analysis, strain NLS-1 was assigned to Aspergillus section Flavi and designated as Aspergillus sp. NLS-1. Bioassays revealed that the isolate exhibited high virulence against third-instar N. lugens nymphs; the highest concentration of 1 × 108 conidia/mL resulted in 97.22% corrected mortality by 9 days post-inoculation and a median lethal time (LT50) of 4.13 days. Scanning electron microscopy delineated the infection process, confirming firm conidial adhesion to the cuticle, followed by germination, hyphal proliferation, and eventual host colonization. Furthermore, fungal infection significantly altered the nymphs' bacterial community structure, notably affecting the relative abundances of Acinetobacter and Serratia. These findings position Aspergillus sp. NLS-1 as a promising biocontrol agent and suggest that its pathogenicity may be mediated through the disruption of the host's microbiota, providing new insights for the integrated management of N. lugens.