Spittlebugs of Mediterranean Olive Groves: Host-Plant Exploitation throughout the Year

Spittlebugs are the vectors of the bacterium Xylella fastidiosa Wells in Europe, the causalagent of olive dieback epidemic in Apulia, Italy. Selection and distribution of dierent spittlebugspecies on host-plants were investigated during field surveys in 2016-2018 in four olive orchards ofApulia and Liguria Regions of Italy. The nymphal population in the herbaceous cover was estimatedusing quadrat samplings. Adults were collected by sweeping net on three dierent vegetationalcomponents: herbaceous cover, olive canopy, and wild woody plants. Three species of spittlebugswere collected: Philaenus spumarius L., Neophilaenus campestris (Fallén), and Aphrophora alni (L.)(Hemiptera: Aphrophoridae). Philaenus spumarius was the predominant species both in Apulia andLiguria olive groves. Nymphal stages are highly polyphagous, selecting preferentially AsteraceaeFabaceae plant families, in particular some genera, e.g., Picris, Crepis, Sonchus, Bellis, Cichorium, andMedicago. Host-plant preference of nymphs varies according to the Region and through time andnymphal instar. In the monitored sites, adults peak on olive trees earlier in Apulia (i.e., duringinflorescence emergence) than in Liguria (i.e., during flowering and beginning of fruit development).Principal alternative woody hosts are Quercus spp. and Pistacia spp. Knowledge concerning plantselection and ecological traits of spittlebugs in dierent Mediterranean olive production areas isneeded to design eective and precise control strategies against X. fastidiosa vectors in olive groves,such as ground cover modifications to reduce populations of spittlebug vectors.