Interaction networks between spittlebugs and vegetation types in and around olive and clementine groves of Corsica; implications for the spread of Xylella fastidiosa

The bacterium Xylella fastidiosa (Xf) is a major threat to European agriculture and notably to the olive and Citrus industry. It is transmitted by xylem-feeding insects, whose plant-feeding preferences still require investigation in European agroecosystems. Here we studied olive and clementine groves of the oriental plain of Corsica. Insect-vegetation type interaction networks for nymphs and adults of xylem-feeding insects were investigated three times a year during two years in and around crops. Networks were dominated by the Philaenus spumarius – Cistus monspeliensis interaction and were similar for olive and clementine groves, despite differences in plant communities of the ground vegetation and agricultural practices. To a lesser extent, Dittrichia viscosa was also a suitable feeding plant for P. spumarius, the main vector of Xf in Europe. Neophilaenus campestris was associated with grove ground vegetation, whereas Lepyronia coleoptrata and Aphrophora alni exhibited no or weak association with any of the target vegetation types. All species occurred on olive and clementine foliage in similar low abundance. Our results suggest that soil tillage in spring would be less efficient than in Italy to control P. spumarius. Instead, removing C. monspeliensis bushes from the close vicinity of groves could reduce risk of spread of Xf to crops. Finally, conserving D. viscosa in olive groves as a biological control strategy against the olive fruit fly is rather counter-productive as it maintains populations of P. spumarius under susceptible crops. Overall, our study shows that management strategies should be designed in relation to local insect-plant interaction networks that should be investigated in both cultivated areas and their immediate environment.