Cankers - Trees and Shrubs

Large canker on the trunk of a beech tree

There are a large number of cankers that cause dieback on trees and shrubs. These are more common on stressed plants due to poor maintenance or site problems. Young cankers are slightly darker in color than adjacent healthy bark and appear slightly sunken. As cankers enlarge they kill the living woody tissue within the branch or trunk.

 
Cytospora canker 

Lower branches dying from Cytospora

Seiridium canker on branch of 
Leyland Cypress

Canker growth may cause the bark along
the edges to crack and fall away, exposing
the dead wood underneath

Canker growth may cause the bark along the edges to crack and fall away, exposing the dead wood underneath. After a canker enlarges enough to girdle a branch or trunk, the portion beyond the canker dies. Small twigs are killed more quickly than larger branches. Symptoms may include progressive upper branch dieback, disfigured branch growth, or target-shaped areas on trunks with concentric rings of dead bark. Examples of fungi that cause cankers in the landscape include Nectria, Cytospora, Phomopsis, Monochaetia, Fusarium, and Botryosphaeria.

Canker on a rose cane


Canker on a tree trunk

Management strategies

There are no chemical controls for cankers and they cannot be stopped once they become extensive. The only control measures available are to remove affected branches and prune back to healthy wood. Drought stressed plants should be watered during dry weather to promote better tree vigor.

Additional Resource

Cytospora Canker of Spruce