Beauveria bassiana B094 as a dual‐action biocontrol agent: Combining direct pathogenicity and endophytic colonization against Spodoptera exigua in sweet corn

This study investigates the endophytic biocontrol potential of Beauveria bassiana strain B094 against Spodoptera exigua in sweet corn through laboratory, greenhouse and field assessments. Laboratory virulence screening identified B094 as pathogenic to S. exigua , inducing 99.8% mortality and exceeding 75% infection in 1st‐ and 3rd‐instar larvae at 1 × 10 8 spores/mL. The LC 50 for 3rd‐instar larvae was 4.8 × 10 5 spores/mL. B094 established endophytic colonization in sweet corn varieties Zhetian 19 and Zaotiannuo 211 via seed inoculation. Colonization peaked at 7 d after emergence (DAE), with leaves exhibiting markedly higher frequency and density (91.1%, 1367 ± 95 CFU/g) than stems (40%, 353 ± 12 CFU/g) and roots (37.8%, 93 ± 9 CFU/g), then progressively declined to 24.3% in leaves and below 17.3% in stems and roots by 28 DAE. Feeding bioassay demonstrated that leaves from colonized plants at 14−21 DAE significantly increased larval mortality and disrupted development. Greenhouse and field trials confirmed efficacy, with inoculated plants exhibiting less foliar damage than controls and similar colonization patterns and biocontrol effects across varieties. Rhizosphere microbiome analysis revealed community shifts after B094 colonization. Bacterial genera often associated with plant growth promotion or biocontrol (e.g., Bacillus , Gemmatimonas ), increased by 22.5% and 81.6%, whereas fungal genera commonly reported as plant pathogens (e.g., Gibberella and Fusarium ), decreased by 87.7% and 78.1%, respectively. Our findings establish B. bassiana B094 as a dual‐action biocontrol agent against S. exigua , combining direct pathogenicity with endophytic effects, supporting seed‐treatment as an environmentally friendly strategy for sustainable pest management in sweet corn systems.