Infection produces a dark, sunken, dead area on the bark, known as a canker. The lower portion of a Spruce is usually affected first. The disease then slowly progresses up the tree. Cankers on White and Colorado Spruce usually start at the base of a lower branch, eventually killing the entire branch. Less commonly, Norway Spruce is subject to trunk cankers which can girdle the entire tree.
Shallow roots are also susceptible to the canker.
Symptoms of Cytospora canker include browning and defoliation of needles on affected branches and a conspicuous white resin flow from the infected area. Prevention is the key to control of Cytospora canker. Maintain the vigor of mature Spruce by watering regularly. Avoid wounding trees, especially during wet weather. Sterilize pruning tools with rubbing alcohol, full-strength liquid household cleaner, or dilute bleach after pruning each tree to prevent transmission of the disease.