Beauvericin production by endophytic and epiphytic Beauveria bassiana in peach (Prunus persica) and implications for insect biocontrol

<i>Beauveria bassiana</i> (Balsamo) Vuillemin is a well-known entomopathogenic fungus that occupies diverse ecological niches, including soilborne, epiphytic, and endophytic habitats. Its capacity to function as an endophyte has received growing interest in potential applications for sustainable pest management, particularly in woody perennial systems where delivery and persistence of biological control agents are challenging. This study investigated endophytic colonization of peach (<i>Prunus persica</i> Batsch) seedlings by <i>B. bassiana</i> and quantified production of the insecticidal secondary metabolite beauvericin (BEA) in and on plant tissues. Seedlings were inoculated via foliar spray or soil drench. Fungal recovery was assessed from leaf, stem, and root tissues. Colonization patterns indicated systemic movement, however foliar spray increased recovery from leaf tissues and soil drench increased recovery from roots over time. BEA concentrations varied significantly by tissue type, inoculation method, and surface sterilization status. The highest levels were detected in non-surface-sterilized leaves of foliar-sprayed plants, measured two weeks post-inoculation. Surface sterilization prior to extraction significantly reduced detected concentrations, suggesting that BEA is primarily produced by epiphytic fungal growth. Larval bioassays with <i>Tenebrio molitor</i> L. revealed increased mortality associated with foliar-sprayed tissues, aligning with observed BEA levels and suggesting localized insecticidal activity. These findings demonstrate that the spatial dynamics of fungal colonization and metabolite localization are critical considerations for the effective deployment of <i>B. bassiana</i> in biocontrol strategies. Further research is needed to determine how environmental factors, host physiology, fungal strain, and time influence secondary metabolite production in and on plants treated with <i>B. bassiana</i>.