Preliminary data on the phenology and the distribution Philaenus italosignus in Apulia (southern Italy)

Spittlebugs received in the past few years major attention by the research community and farmers, as consequence of the introduction and spread in Europe of the quarantine bacterium Xylella fastidiosa. Spittlebugs represent in fact the predominant xylem feeders in Europe. Indeed, both Philaenus spumarius L. and Neophilaenus campestris (Fallén) have been demonstrated to be competent vector and be quite common in olive groves in the Italian region of Apulia where a highly pathogenic bacterial strain is decimating this important crop species. To further investigate the risks posed by other species of spittlebugs, the phenology, host preference and distribution of Philaenus italosignus Drosopoulos & Remane (Aphrophoridae) was also investigated through a large scale field survey carried out in the region. P. italosignus was first described in Apulia in 2000 and then also reported from Sicily, Lazio and more recently from Tuscany; in the latter case associated with an outbreak of X. fastidiosa. Given the continuous expansion of the Xylella-epidemic in Apulia towards areas where beside olives different crops are cultivated, and the notion that P. italosignus is also a competent vector of X. fastidiosa, from 2017 to 2019 surveys were focused to document the presence and occurrence in different areas, to characterize the phenology and juvenile morphometry. Areas with abundant presence of Asphodelus spp., on which juveniles develop, were prioritized for surveys. The data collected showed that (i) the density of individuals per m2 can be particularly high, reaching even 400 individuals/m2; (ii) even if Asphodelus spp. was abundant in some locations, no specimens of this species could be recorded, as for example in the province of Lecce. Moreover, the results of periodic monitoring carried out in locations at different altitudes have also shown, as expected, that the juveniles appeared about 7 days earlier in the coastal area than those located in the inland of the region. The comparison of the phenology of P. italosignus with that of the most common species, P. spumarius, showed that juveniles of P. italosignus appear 20-30 days earlier than P. spumarius, and consequently adults are captured 10-25 days earlier (depending on the vintage). With reference to the adults, unlike the juveniles, they are relatively polyphagous, feeding in particular on cherry trees. One aspect to highlight is that although there are ecological niches with a very high population density of juveniles, no correlation was retrieved between juvenile population density and capture of adults. Generally, a very low number of adults (1 individual/sample unit) if not any could be collected by sweep net. It would therefore be interesting to study the population dynamics of adults, in order to better understand their dispersion or disclose the "refuge" sites. It will also be useful to determine the climatic and/or ecological conditions that delimit the areas of diffusion of this species.