NATIVE RANGE: North America

FIRST FINDING IN SLOVENIA: not yet found in Slovenia

PATHWAYS: transported with branches, wood and bark; spores secondary spread spontaneously. 

POSSIBLE TO FIND: year-round

DESCRIPTION: This disease can be recognised by the wilting and drying of leaves. It first appears on some branches but can quickly spread to the entire canopy. Infected trees die in one to two years. On the bark of infected trees, exit holes of walnut twig beetles (Pityophthorus juglandis) can be found, which are less than 1 mm wide. If the bark is peeled off with a knife, decaying brown bark is visible in the form of numerous lenticular necroses which are up to 20 cm long. In the middle of these necrotic lesions we can find beetle tunnels, and during the vegetation season usually also tiny beetles, 1,5-2 mm.

HOST PLANTS: Primary host plants are black walnut (Juglans nigra) and common walnut (J. regia).

STATUS: In Europe only reported from Italy.

SIMILAR SPECIES: No other species cause similar damage symptoms of damage on walnut trees.

SOURCE: Field Guide to Invasive Alien Species in European Forests