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For non-native tree species with an origin outside of Europe a detailed compilation of enemy species including the severity of their attack is lacking up to now. We collected information on native and non-native species attacking non-native trees, i.e. type, extent and time of first observation of damage for 23 important non-native trees in 27 European countries. Our database includes about 2300 synthesised attack records (synthesised per biotic threat, tree and country) from over 800 species. Insects (49%) and fungi (45%) are the main observed biotic threats, but also arachnids, bacteria including phytoplasmas, mammals, nematodes, plants and viruses have been recorded. This information will be valuable to identify patterns and drivers of attacks, and trees with a lower current health risk to be considered for planting. In addition, our database will provide a baseline to which future impacts on non-native tree species could be compared with and thus will allow to analyse temporal trends of impacts., (© 2021. The Author(s).)

Host preference of root endophytes of the three European tree species of Norway spruce ( Picea abies ), common ash ( Fraxinus excelsior ), and sycamore maple ( Acer pseudoplatanus ) were investigated in two forest stands near Zurich, Switzerland. The focus was placed on members of the Phialocephala fortinii s.l. (sensu lato)- Acephala applanata species complex (PAC), as well as other dark septate endopyhtes (DSE). PAC species were identified based on 13 microsatellite loci. Eleven PAC species were found, with Phialocephala helvetica , P. europaea being the most frequent. All but cryptic species 12 (CSP12) preferred Norway spruce as a host. Though very rare in general, CSP12 was most frequently isolated from maple roots. Regarding the abundant PAC species, P. helvetica and P. europaea , the preference of spruce as a host was least pronounced in P. europaea , as it was also often isolated from ash and maple. It is the first record of PAC found on common ash ( Fraxinus excelsior ). Cadophora orchidicola , a close relative of PAC, has frequently been isolated from ash. Various species of the Nectriaceae ( Cylindrocarpon spp.) have often been isolated, particularly from maple roots. By comparison, Pezicula spp. ( Cryptosporiopsis spp.) was found to be abundant on all three hosts. Phomopsis phaseoli exhibits a clear preference for spruce.