First report of Juglans ailanthifolia in Italy and Switzerland
Juglans ailanthifolia (Juglandaceae) is native to Japan and the Russian Far East (Sakhalin Island). The species is invasive in New Zealand and Australia. In this region, J. ailanthifolia can grow along waterways, disturbed forests and shrubland, in pastures and along roadsides. The species can spread naturally by seeds which are spread by water and animals and also by humans who can dump garden waste that contains viable seeds. J. ailanthifolia can compete with native vegetation and displace native biodiversity and it can block waterways. In the EPPO region, J. ailanthifolia has previously been reported as a garden escapee from Germany. Juglans ailanthifolia was first found in the Canton of Ticino, Switzerland in 2019. The species was found in the areas of Bellinzona and Mendrisio, in moist lowland environments. The two largest sites are located in Gnosca and Novazzano. The former site is spread over 1 ha, and appears to be an abandoned plantation. There are adult J. ailanthifolia trees over 20 m tall with a trunk diameter of up to 45-50 cm, suggesting that they are 60-70 years old. The latter site is more extended, as mature individuals are sparsely spread along a small valley for at least 3 km. In Italy, J. ailanthifolia occurs in Lombardy, and the individuals here were previously misidentified as another casual alien species, J. cinerea. It was only in 2020 that individuals at a site in Val Seriana (Piario) were checked and subsequently identified as J. ailanthifolia. There appears to be a relatively limited spread of this tree in both Italy and Switzerland and thus at present it does not appear to be exhibiting invasive behaviour.
A new global distribution map has been added to EPPO Global Database: https://gd.eppo.int/taxon/IUGAI/distribution.
Sources
Marazzi B, Rosselli A, Galasso G, Eggenberg S (2021) Juglans ailanthifolia A new alien walnut tree species naturalised in Switzerland and Italy. Bollettino della Società ticinese di scienze naturali 109, 57-68.