Distribution, adult phenology and life history traits of potential insect vectors of Xylella fastidiosa in Belgium

Hasbroucq, Séverine [UCL] Casarin, Noemi [UCL] Czwienczek, Ewelina Bragard, Claude [UCL] Jean-Claude GRÉGOIRE

The xylem-inhabiting phytopathogenic bacterium, Xylella fastidiosa, is mainly transmitted in Europe by the spittlebug (Aphrophoridae) Philaenus spumarius. In Belgium, other xylem-sap feeding Hemiptera (Aphrophora alni, Aphrophora salicina, Cercopis vulnerata, Cicadellaviridis) are also present and considered as potential vectors. The distribution, adult phenology and host plants in Belgium of these five species were analysed, using information from the Royal Belgian Institute of Natural Sciences collections, the naturalist web site Observations.be,and our own field data collections in 2016-17. Adults of the highly polyphagous A. alni, C.vulnerata, C. viridis, and P. spumarius were found in all the ecological regions of Belgium; A.salicina was less widely distributed and, in particular, was absent from the Ardennes and Lorraine, probably due to its narrower specificity to Salix spp. The C. vulnerata adults were collected mostly in May, whilst the other species' adults were found mostly from April to October with a peak in July for A. alni, in August for A. salicina and C. viridis, in May and August for P. spumarius. An egg winter diapause was observed in P. spumarius and A. salicina, whose eggs hatched only after overwintering under natural conditions. On the contrary, several successive generations of C. viridis could be reared under laboratory conditions. These last three species have five nymphal instars. In limited quantitative field samplings, C. viridis was found to be locally very abundant (up to 37,000 eggs/m2), and egg parasitism by a Mymarid wasp, Anagrus incarnatus, reached nearly 12%.