spruce branches dying - cytospora canker symptoms

Cytospora canker symptoms on blue spruce. Photo: Joseph OBrien, USDA Forest Service, Bugwood.org

Updated: March 9, 2021

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.

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.
dying branches of redbud tree - botryosphaeria canker symptoms

Botryosphaeria canker symptoms on Eastern redbud. Photo: Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org

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.