Dothiorella canker

Pathogen and disease type. The pathogen responsible for the disease is the fungus Dothiorella aromatica (often associated with Botryosphaeria dothidea), classified within the Dothideomycetes class. This fungus acts as an opportunistic pathogen that triggers bark necrosis and vascular decay, ultimately leading to branch dieback and overall tree decline.

Host plants. Dothiorella aromatica has a broad host range, affecting various broadleaf and coniferous trees. It is particularly damaging to commercial fruit orchards, including apple and walnut trees, as well as several species of ornamental trees and shrubs used in landscaping, where environmental conditions favor the fungus.

Symptoms and signs of infection. The primary visual symptoms include sunken, necrotic areas or cankers on the bark of stems and branches. During humid weather, the surface of these cankers often shows small, dark, pimple-like fruiting bodies. Internally, the sapwood may exhibit dark discoloration, which obstructs water and nutrient flow, causing the foliage to wilt and the affected branches to dry out prematurely.

Conditions for development and severity. The disease thrives under warm, humid conditions and is often exacerbated by plant stress, such as drought, winter injury, or poor site management. Spores are disseminated by rain splash, wind, and pruning tools. The economic impact is significant, as the infection can lead to reduced fruit yield, disfigurement of trees, and eventual death of the entire plant if left unmanaged.

Control and prevention measures. Effective management of the disease requires an integrated approach to maintain tree health and reduce inoculum levels:

• Regularly prune and remove diseased branches, ensuring cuts are made well into healthy tissue.
• Sanitize all pruning equipment thoroughly between trees to prevent cross-contamination.
• Promote optimal plant growth through balanced fertilization and appropriate irrigation to reduce susceptibility to stressors.
• Apply protective copper-based fungicides or systemic fungicides during early spring or after pruning to prevent infection of fresh wounds.