Philaenus spumarius and Neophilaenus campestris as efficient insect vectors for Xylella fastidiosa in Majorca (Spain).

Xylella fastidiosa is a pathogen xylem-limited bacterium detected in the Balearic Islands (Spain) in 2016 and transmitted by xylem-sap feeders insect vectors. The major potential vectors described in the Balearics are the spittlebugs Philaenus spumarius and Neophilaenus campestris (Aphrophoridae).  In order to assess the potential transmission efficiency of these vectors, two types of transmission tests were conducted. In the first type, we assessed the natural infectivity of the vectors. For this, P. spumarius and N. campestris adults were collected from the field and kept in groups of three to five insects in alfalfa (Medicago sativa) for 96 hours for the inoculation access period (IAP). The infection status of alfalfa plants was checked at 15, 30, 45 and 60 days after IAP. In the second type of experiment, uninfected adults were caged on X. fastidiosa infected grapevine and almond plants for 96 hours of acquisition access period (AAP) and then transferred onto healthy plants of alfalfa as described for the first type of experiment. In both experiments, the presence of X. fastidiosa in plants and insects was established by qPCR analysis. In the first experiment,  21.7% of P. spumarius and 15.6% of N. campestris (field collected) tested positive for X. fastidiosa.  About 35% of the plants exposed to P. spumarius and 43% of those exposed to N. campestris were infected. In the second experiment, 3.8% of P. spumarius acquired the bacteria from infected vine plants and 14,3% of the alfalfa plants resulted positive to X. fastidiosa after the IAP. In conclusion, both species of spittlebugs found in the Balearics are able to transmit X. fastidiosa in laboratory trials. However, its comparative epidemiological role could be different due to host preference, distribution and abundance.