NATIVE RANGE: East Asia: China and Japan

FIRST FINDING IN SLOVENIA: 1950

PATHWAYS: transported with saplings and wood, secundary also by insects and wind

POSSIBLE TO FIND: year-round

DESCRIPTION: This tree disease is typically virulent, but can appear in a non-virulent form when the fungus is infected by a virus. The virulent form progresses rapidly, leading to the dieback of infected trees. The first symptom is a change in the colour of the bark, which becomes darker with orange spots. Below the bark, there are fan-shaped mycelia, while pin-sized orange to brick red fruiting bodies develop on the external surface. The hypovirulent form causes only minor cracks in the bark and minor hypertrophy of branches and trunk.

HOST PLANTS: Sweet chestnut (Castanea sativa). Oaks (Quercus spp.) may be infected when they grow in the vicinity of infected chestnuts.

STATUS: The disease is present across the entire distribution range of sweet chestnut. Widespread throughout Slovenia, but in varying intensity. In some areas the Hypovirus CHV1 affects Blight of chestnut. In these areas Blight of chestnut has a reduced virulence. 

SIMILAR SPECIES: Gnomoniopsis smithogilvyi causes chestnut brown rot on chestnut fruits and can also result in damage to bark. It has grey fruiting bodies and white spores and is progressing more slowly than the chestnut blight.

SOURCE: Field Guide to Invasive Alien Species in European Forests