Endophytic colonization and epiphytic presence of Metarhizium brunneum alter the feeding behavior of the Xylella fastidiosa vector Philaenus spumarius

• DOI: 10.1007/s10340-026-02015-3

Philaenus spumarius represents the primary vector of the bacterium Xylella fastidiosa in Europe; hence, control measures are directed toward it, with a need for alternatives aligned with the agricultural sustainability criteria. Entomopathogenic ascomycetes (EA) show promise by infecting P. spumarius via endophytic colonization, though their sublethal effects on behavior remain understudied. This study assessed the effects of Metarhizium brunneum strain EAMa 01/58-Su on P. spumarius survival and feeding behavior, using the Electrical Penetration Graph technique. We provide the first evidence of endophytic colonization of olive plants by EA, occurring in both treated and distant untreated leaves. Foliar application enabled the dual establishment of M. brunneum as both epiphytic and endophytic, significantly disrupting vector feeding. Insects fed on M. brunneum sprayed leaves showed a more total and unsuccessful probing events, longer non-probing (np) periods, and reduced xylem contact (Xc) duration. Additionally, successful xylem probing (with xylem ingestion) was significantly delayed. Interestingly, a reduction in waveform N events and their duration in M. brunneum—non-sprayed leaves was detected, suggesting a systemic effect of the fungal colonization on the plant preference by the vector that could ultimately disrupt Xf retention mechanisms. In contrast, the drench application of M. brunneum in the olive saplings did not result in endophytic colonization or significant effects on the insect behavior compared with control plants. These findings provide the basis for future experiments on Xf transmission and support the potential of M. brunneum as a biocontrol agent beyond its conventional use against vector populations on cover crops.

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