Survey of Auchenorrhyncha in the Salento peninsula in search of putative vectors of Xylella fastidiosa subsp. pauca CoDiRO strain

Xylella fastidiosa (Xf) was identified in September 2013 in olive trees affected by the Olive quick decline syndrome (OQDS) in the Salento peninsula (southern Italy) and denoted Xf strain CoDiRO. Xf is comprised of a group of genetically diverse bacteria in the class Gammaproteobacteria that causes severe plant diseases in many crops and ornamentals. The bacterium is acquired and transmit- ted by xylem-sap feeding hemipterans such as sharpshooter leaf- hoppers (Cicadellidae, Cicadellinae), froghoppers and spittlebugs (Aphrophoridae and Cercopidae) and, possibly, cicadas (Cicadidae and Tibicinidae). Due to the rapid spread and devastation associ- ated with OQDS, a survey of candidate vectors of Xf was conducted from September 2013 in the Gallipoli area in accordance to a EFSA list (EFSA, 2013). Four candidate vector species were identified: (i) Aphrophoridae: Philaenus spumarius L. and Neophilaenus camp- estris Fallen; (ii) Cercopidae: Cercopis sanguinolenta Scopoli; (iii) Ci- cadidae: Cicada orni L. Among these, only P. spumarius, the meadow spittlebug, was experimentally proven to be a vector of X. fastidiosa strain CoDiRO. A high percentage of meadow spittlebugs collected from OQDS-affected orchards, from May to September 2014, tested positive for X. fastidiosa by PCR. Transmission to periwinkle plants was successful. Laboratory tests, so far limited to the Philaenus-ex- posed periwinkle seedlings, will be extended to the entire panel of the host plants (olives, grapes, citrus, oleander and Prunus spp.) that were exposed to infectious spittlebugs. Further ongoing experiments include Xf-free spittlebugs that were allowed to feed on infected olives and other hosts plants prior to transferring onto receptor host plants. The results so far obtained have shown that olive is a source of inoculum from which P. spumarius is able to acquire the bacte- rium and transfer it to other olives. These data strongly suggest that the main vector of Xf in the area of it occurrence is P. spumarius. Transmission tests carried out with other xylem sap feeders found in the OQDS area are also discussed.