NATIVE RANGE: North America

FIRST FINDING IN SLOVENIA: not yet found in Slovenia

PATHWAYS: transported by people with tree cutting tools. Secondary spreading by wind and insects

POSSIBLE TO FIND: year-round

DESCRIPTION: Infected trees can be recognised from a distance because parts of the canopy die back during the vegetative season. Usually, leaves of affected trees are smaller compared to those of healthy plane trees. Infected areas of the bark appear as dark grey patches with a paler edge. The wood underneath these patches is dark brown to purple. These lenticular necrotic patches may coalesce to form extensive lesions. In cross-sections of infected wood, a bluish staining is visible, which extends radially into the sapwood.

HOST PLANTS: This fungus infects all plane species (Platanus spp.).

STATUS: The disease, which is listed as a quarantine pest, is especially widespread across the Po-plain in Italy.

SIMILAR SPECIES. No other species causes rapid dieback in plane trees, combined with a dark brown to purple staining of the wood. Drying of leaves and shoots and dieback of bark can also be caused by anthracnose of plane (Apiognomonia veneta) or phytophthoras. In these cases, the infection usually spreads upwards from the ground. See the facing page for example photographs.

SOURCE: Field Guide to Invasive Alien Species in European Forests