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Alder (Alnus spp.) - Canker and Stem Diseases
Cause There is little information on cankers of birch in the PNW. Few samples have been sent into plant clinics indicating it is not a major issue for these trees. The OSU Plant Clinic has found Cytospora sp., Nectria sp. and Melanconis stilbostoma (formerly Melanconium botulinum). Botryosphaeria canker has been found in Washington. Trees with cankers are usually stressed by drought, wind damage, nutrient imbalance, flooding, soil disturbance, snow and ice damage, and other severe conditions. Cankers generally cause only minor dieback but may be indicative of poor health.
Symptoms Young cankers appear darker and slightly more sunken than adjacent healthy bark. As they enlarge, they kill living woody tissue within the branch or trunk. Canker growth may cause the bark along the edges to crack and fall away, exposing dead wood underneath. After a canker enlarges enough to girdle a branch or trunk, the portion above the canker dies. Small twigs are killed more quickly than larger branches. Symptoms may include progressive upper branch dieback, disfigured branch growth, and target-shaped areas with concentric rings of dead bark on trunks.
Cultural control
- Select good trees for the site location.
- Keep trees in good vigor and avoid wounding. Stressed trees should be fertilized and watered during dry periods, to promote better tree vigor.
- Remove and destroy dead or severely cankered branches or trees.
Reference Fan, X., Du, Z., Liang, Y. and Tian, C. 2016. Melanconis (Melanconidaceae) associated with Betula spp. in China. Mycological Progress, 15:40.