Elm canker

Elm canker, caused by the fungal pathogen Tubercularia ulmea, is a destructive disease primarily affecting the branches and trunks of susceptible trees. This type of necrosis disrupts the vascular system, preventing the flow of nutrients and water, which ultimately leads to the dieback of affected parts. It acts as a opportunistic pathogen, thriving in tissues that are already weakened by environmental stresses.

This fungus is particularly well-known for attacking various species of Elms (Ulmus). Additionally, it can infect members of the Liquidambar genus, such as the Sweet Gum tree. Because these trees are frequently used in urban landscapes and street plantings, the presence of this fungus can significantly reduce the ecological and aesthetic value of a green space.

The visual signs of infection include the development of depressed, discolored lesions on the bark. As the fungus matures, it produces distinct coral-pink or reddish pustules, which are the fruiting bodies of the organism. When the infection encircles a branch, it causes the canopy above that point to wilt and die, a condition often described as branch flagging.

Development of the disease is heavily influenced by high humidity levels and temperature fluctuations that cause bark damage. Frost cracks, sunscald, and improper pruning wounds provide easy entry points for the fungal spores. Spores are primarily disseminated by splashing rainwater, wind, and movement of infested wood, making early detection critical for containing local outbreaks.

Control measures primarily focus on sanitary practices. All infected branches must be pruned well below the site of the canker to ensure that no mycelium remains in the wood. It is essential to sanitize pruning tools with alcohol or a bleach solution between cuts to prevent mechanical spread. Furthermore, maintaining tree vigor through adequate watering and balanced fertilization helps the tree naturally resist fungal invasion.

• Prune and remove infected branches immediately
• Sanitize tools with disinfectant between each cut
• Protect stems from sunscald and winter injury
• Encourage tree health through proper irrigation