From soil to target: investigating the role of native entomopathogenic fungi as biocontrol agents against Scaphoideus titanus Ball (Hemiptera: Cicadellidae) in grapevines

Entomopathogenic fungi (EPF) are promising biological control agents for the integrated pest management of Scaphoideus titanus Ball, the principal vector of Flavescence dorée phytoplasma in European vineyards. This study assessed the diversity, abundance, pathogenicity, and endophytic colonization ability of native EPF isolated from vineyard, woodland, and fallow field soils in the Piedmont Region (northwestern Italy). A total of 151 EPF isolates were recovered using selective media plating and the Galleria bait method and identified by ITS sequencing. Of the 14 species identified, eight belonged to genera with well-established entomopathogenic activity, whereas the remaining six have been less consistently associated with entomopathogenicity in the literature. The most frequently recovered species were Metarhizium anisopliae, Metarhizium robertsii, and Purpureocillium lilacinum. Pathogenicity assays revealed pronounced strain-specific differences against S. titanus. M. anisopliae BP1e and M. robertsii BP1k caused the greatest mortality, reducing insect survival to 27.2% and 40.2% at 12 days post-treatment, respectively, compared with 46.3% for the reference strain Beauveria bassiana ATCC 74040. Endophytic colonization assays also showed marked variation among strains. P. lilacinum CaS1a achieved the highest and most persistent colonization of treated leaves, reaching 79%, whereas Metarhizium isolates, particularly M. anisopliae BP1r, established consistent but more localized colonization. Penicillium citrinum CaS1d showed the highest colonization of untreated leaves (38.5% at 14 days post-treatment), suggesting greater capacity to spread beyond the application site. Beauveria isolates exhibited moderate colonization. These findings highlight the potential of indigenous EPF to combine direct pathogenicity with persistent endophytic establishment, supporting their integration into sustainable grapevine pest management. Future studies should optimize fungal formulations and evaluate single and combined strain applications under field conditions.