Cytosporina canker

Cytosporina canker is a destructive fungal disease caused by the pathogen Cytosporina ludibunda. It primarily targets the bark and cambium layers of woody plants, leading to localized necrosis that can eventually girdle branches or entire trunks if left untreated.

The disease is particularly associated with Elm species (Ulmus), though it can affect other ornamental and forest trees. It is often found in both urban landscapes and nurseries, posing a significant risk to trees already weakened by drought, transplant stress, or poor environmental conditions.

Early symptoms include the appearance of discolored, sunken areas on the bark. As the infection progresses, these areas exhibit cracking and peeling of the bark, revealing dead tissues underneath. Small black fruiting bodies of the fungus (pycnidia) often protrude through the bark surface, serving as a diagnostic visual marker for the disease.

The development and spread of Cytosporina are strongly correlated with periods of high humidity and moderate temperatures. The fungus enters the host through wounds, such as pruning cuts, frost cracks, or sites damaged by insects. Once established, the pathogen produces spores that are easily disseminated by wind and splashing rain, allowing the disease to propagate within a canopy or between adjacent trees.

Management of Cytosporina canker relies heavily on sanitation and preventive care. Infected branches should be pruned back to healthy wood, with tools disinfected between cuts to prevent cross-contamination. Promoting tree vigor through adequate irrigation, proper fertilization, and protection against physical injury are essential strategies to minimize the impact of the disease and prevent new infections.