Canker

Diseases

A localized dead area on the bark or cambium of a tree trunk or branch, caused by fungal or bacterial infection, that often appears as sunken, discolored, or cracked bark.

A canker is a discrete area of dead bark and cambium on a tree's trunk or branches. Cankers are caused by various fungal and bacterial pathogens that infect through wounds, branch stubs, or stressed bark. They appear as sunken, flattened, or swollen areas on the bark surface, often with cracked, discolored, or peeling bark at the margins. Some cankers ooze sap or resinous material.

Cankers damage trees in several ways. They kill the cambium and bark in the affected area, disrupting nutrient and water transport in the phloem. If a canker expands to girdle (encircle) a branch or trunk, everything above the girdled point dies. Cankers also create entry points for wood decay fungi, compromising structural integrity. Annual cankers complete their expansion in one season, while perennial cankers enlarge progressively year after year.

Management of cankers begins with prevention through maintaining tree vigor and minimizing wounds. Stressed trees, particularly those suffering from drought, are far more susceptible to canker diseases. For isolated cankers on branches, pruning well below the infected area into healthy wood can eliminate the pathogen. Trunk cankers are more challenging; maintaining the tree's overall health to allow it to wall off the infection is often the primary strategy. There are no effective chemical treatments for most canker diseases.