Cytospora Canker
Cytospora / Leucostoma spp.
Range: Throughout the United States; attacks stressed, drought- or winter-injured treesSee it on the alert map
Symptoms & signs
- On spruce, lower branches die first and the dieback progresses upward, leaving brown, brittle limbs
- sunken, discolored cankers on branches and trunk
- bluish-white sap or amber resin oozing and crusting over cankers
- pinhead black fruiting bodies in dead bark
- on poplars and willows, girdling stem cankers that wilt branches
Treatment & management
- No effective fungicide — manage by keeping trees vigorous with proper watering (especially during drought) and mulch, since the fungus is opportunistic on stressed tissue
- Prune out cankered limbs in dry weather, cutting well into healthy wood and disinfecting tools
- Avoid wounding and winter injury
- Replace badly affected trees with adapted species
Host species
Common questions
Why are the lower branches of my blue spruce dying from the bottom up?
That bottom-up branch death, often with bluish-white resin crusts on the bark, is typical cytospora canker. It attacks stressed spruces; keep the tree watered and prune out dead limbs in dry weather.
Can I spray to cure cytospora canker?
No fungicide reliably controls it. Because the fungus exploits stressed trees, management is cultural: reduce stress with water and mulch, remove cankered wood cleanly, and avoid wounding the bark.
Related diseases
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