Initial Insights into Spittlebug-Mediated Spread of Xylella fastidiosa subsp. fastidiosa Sequence Type 1 in Southern...

Xylella fastidiosa subsp. fastidiosa sequence type 1 was recently found in one of the most economically important European table grape districts in southeastern Italy. Data on insect vectors involved in the bacterium's spread are urgently needed to inform timely management strategies. A survey of potential vector species was conducted from April to October 2024 in five table grape vineyards adopting the "tendone" training system and five mixed plots (wine grapevines, olives, almonds, and other plants) located in the municipality of Triggiano (Bari, Italy). We collected data on (i) presence and abundance throughout the year of xylem sap-feeding species (i.e., competent vectors of the bacterium), (ii) infectious status of plants the insects were collected from, and (iii) vector infectivity throughout the year. Adults were collected mostly on ground cover in late April and readily dispersed toward almond, grapevine, and other species. Almond and grape were the only host species found positive for X. fastidiosa by qPCR. Neophilaenus campestris and Philaenus spumarius were the two vector species competent for the bacterium transmission collected during the survey. Current observations are consistent with the hypothesis suggesting a possible two-step transmission pathway, involving a primary transmission from almond to grape, followed by a secondary grape-to-grape spread. However, these inferences are based on a dataset that is both spatially and temporally restricted, largely as a result of ongoing eradication measures that limit further field surveys and experimental transmission studies. Consequently, these findings should be regarded as provisional, yet they provide useful preliminary insights to support the development of X. fastidiosa containment strategies in European table grape vineyards.