Tree decline caused by exotic Phytophthora pathogens is a serious issue affecting forests around the world. The
presence of Phytophthora has been reported in heavily visited natural forests; however, whether recreational
forests are at higher risk of being attacked by Phytophthora than non-recreational forests has yet to be explored. In this study, we sampled soil from 44 forests in Catalonia (NE Spain) with high or low recreational use that were dominated by chestnut (Castanea sativa), beech (Fagus sylvatica) or cork oak (Quercus suber). A systematic soil sampling of 277 plots in stands of different tree species, predominantly Pinus and Quercus spp., was also conducted across Catalonia to compare soils of recreational forests with high and low recreational use with the baseline incidence of Phytophthora in the region. The putative impacts of the presence of Phytophthora in recreational areas were assessed by measuring tree defoliation and regeneration, and by performing pathogenicity trials using Phytophthora isolates from soil and root samples to inoculate seedlings of tree species growing in the region. The incidence of native and invasive Phytophthora species was higher in chestnut, beech and cork oak forests than in forests of other tree species.
