Hypoxylon canker

The fungus Entoleuca mammata (formerly Hypoxylon mammatum) is the primary causal agent of Hypoxylon canker. This fungal disease is a serious pathogen causing necrotic lesions on the trunks and branches of trees, often leading to structural failure or death of the host plant.

The disease primarily affects species of the genus Populus, including aspens and various hybrid poplars. Because it causes rapid decay and structural weakness, it is considered one of the most destructive diseases in commercial poplar plantations and natural forest stands.

The initial symptoms manifest as discolored, sunken areas on the bark. As the fungus colonizes the inner bark, these areas expand into rough, cracked cankers. Distinctive black, spore-producing structures known as stroma appear on the bark surface, serving as a diagnostic feature for identification.

Development and spread of the fungus are favored by high humidity and stress conditions such as drought, nutrient deficiency, or mechanical injuries. The spores are typically dispersed by wind and rain, infecting the host through wounds, such as those caused by insects, wildlife, or branches breaking off during storms.

Control measures are primarily preventive. These include avoiding the planting of highly susceptible clones, maintaining tree vigor through proper site selection and thinning, and conducting immediate sanitation logging. Removing infected wood helps reduce the inoculum level in the environment, thereby protecting the remaining healthy trees.