NATIVE RANGE: East Asia (China)

FIRST FINDING IN SLOVENIA: after the year 1980

PATHWAYS: Spores of the fungus are spread by Elm bark beetles

POSSIBLE TO FIND: year-round

DESCRIPTION: This fungus causes a disease of water conducting tissues of trees (tracheomycosis). Because water conducting cells are blocked, the branches wilt and eventually die back. The fungus quickly spreads through the wood and infected trees die back within a few years. A typical disease symptom is a brown streaking in the previous year’s annual ring of the wood in the affected branches. The infection is often accelerated by attacks by elm bark beetles (Scolytus spp.). Adult beetles carry the fungal spores on their bodies and in their faeces, which they spread to healthy trees in the surroundings.

HOST PLANTS: All elm species (Ulmus spp.).

STATUS: Widespread throughout Europe. A similar species, Ophiostoma ulmi is present in Slovenia since 1928. This species caused the first die-of of Elm trees. The second species, which currently predominates (O. novo-ulmi), spread to Slovenia after 1980. It caUses massive die-ofs of Elm trees, but affects only mature trees. Younger trees remain unaffected, because bark beetles do not affect them. The disease is occasionally found in all parts of Slovenia. 

SIMILAR SPECIES: Similar symptoms can appear with Verticillium wilt which is caused by fungi of the genus Verticillium (V. alboatrum and V. dahliae).

SOURCE: Field Guide to Invasive Alien Species in European Forests