Dothiorella canker and wilt

Dothiorella canker and wilt, caused by the fungus Dothiorella ulmi, is a destructive disease that affects various species of elm trees (Ulmus). It is characterized by the formation of necrotic lesions on the bark and systemic wilting, often leading to the premature death of branches or the entire tree.

The pathogen specifically infects the bark and sapwood of the elm. Once inside the tree, the fungus interferes with water transport, causing foliage to yellow, curl, and wilt. This process mimics the symptoms of Dutch elm disease, making accurate laboratory diagnosis essential for determining the correct management strategy.

Key symptoms include depressed, discolored patches on the bark, deep fissures, and localized cankers. When the bark is peeled back from affected areas, the inner bark and sapwood often reveal characteristic browning or streaking. The infection can spread rapidly through the canopy if environmental conditions remain favorable.

Disease development is heavily influenced by stress factors such as drought, soil compaction, or physical wounds, which provide entry points for the fungal spores. Once established, the fungus produces pycnidia on the bark, which release spores that spread through wind and splashing rain, especially during wet growing seasons.

Managing the disease requires a combination of sanitation and supportive care. Regular pruning to remove infected branches is the primary control measure, as these branches serve as a reservoir for spores. Maintaining tree vigor through deep watering during dry periods and fertilization can also significantly increase the tree's natural resistance to infection.