Trade-offs between <i>Xylella fastidiosa</i> vector control and conservation of beneficial arthropods in Mediterranean olive groves

Xylella fastidiosa is a xylem-limited gram-negative bacterium responsible for significant crop yield losses worldwide. The sequence type ST53 is recognized as the causal agent of the olive quick decline syndrome, currently threatening olive production in southern Europe, where the olive-to-olive transmission of the bacterium is primarily mediated by a xylem-sap feeder: the meadow spittlebugs Philaenus spumarius. Mandatory control measures, such as the mechanical removal of ground cover, are currently enforced to reduce juvenile vector populations and curb the spread of the pathogen. However, the long-term sustainability of this control strategy in olive groves remains uncertain, particularly regarding its impact on beneficial arthropods. Here, we investigated how seasonal variation in ground cover within olive groves influences abundance of adult X. fastidiosa vectors, beneficial arthropods (i.e., wild pollinators, spiders, and carabids) and predation of P. spumarius eggs in Mediterranean olive groves, while also accounting for surrounding agricultural matrix. Our results showed that the importance of herbaceous vegetation conditions varies across seasons with early spring and spring ground cover emerging as the strongest predictors for most functional groups, while spider populations responded more strongly to summer conditions. Overall, ground cover promoted adult X. fastidiosa vectors, wild pollinators, spiders and carabids depending on the season, whereas complex landscapes enhanced both pollinator activity and egg predation. Intensive ground cover management appears to generate trade-offs between vector control and the conservation of beneficial organisms in Mediterranean agroecosystems, but adjusting the timing of vegetation removal or adopting alternative ground cover management may help to mitigate these conflicts.