Cankers - Trees and Shrubs

 
Large canker on the trunk of a beech tree

Key Points

• 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 causing dieback.
• Management

                        Lower branches dying from Cytospora       Cytospora canker on spruce branch

 Seiridium canker on branch of Leyland    Canker growth may cause the bark along the
Cypress                                                 edges to crack and fall away, exposing dead
                                                            wood underneath 

Canker Problems

• 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 

• 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