Preliminary studies on the seasonal phenology of Philaenus spumarius (L.) in Sardinian cork oak forest ecosystems

Abstract: Xylella fastidiosa subsp. pauca strain 53 is the causal agent of the Olive quick decline syndrome and, since its first report in Europe in 2013, caused the death of more than 21 million olive trees in Apulia (southern Italy). The main vector of this bacterium is Philaenus spumarius L., a widely distributed and polyphagous spittlebug with no previous economic importance, that has gained relevance as a key crop pest and studies on its behavior, biological traits and dynamics have increased exponentially in recent years in the Mediterranean basin. In view of this, field observations were carried out in 2020 in cork oak (Quercus suber L.) woodlands in Sardinia (Italy) to investigate the host preference of P. spumarius nymphs and adults in Mediterranean oak forests and monitor the pest population dynamics. Nymph density was determined as the number of foams/m2, whereas the adult density was estimated as the number of adults/m2 collected by a sweep net. The population density of P. spumarius adults was highest in June and mainly on Cistus monspeliensis, whereas in summer it declined dramatically and was similar on cork oak and C. monspeliensis. Among oak species, P. spumarius seemed to prefer the downy oak (Quercus pubescens Willd.). Our findings indicate the presence allseason long of P. spumarius in Mediterranean oak ecosystems in several host species (Quercus spp., Cistus spp., Carlina sp., Asphodelus ramosus L.), meaning that oak forests may serve as a refuge habitat for the pest. This is of great importance for the possible spread of Xylella infections, as cultivated areas are interspersed with natural vegetation areas and oak stands.