The principal host of the fungal disease, Cytospora canker, is the Colorado blue spruce (Picea pungens) and its cultivars. It may also occur in the Norway spruce (Picea abies), Koster's blue spruce, white spruce (Picea glauca), Douglas fir (Pseudotsuga menziesii) and other spruces planted as ornamentals. Commonly trees are infected when they are 15 to 25 years old and 20 to 40 feet tall.

The most striking symptom of Cytospora canker is the death of individual branches beginning near the bottom of the tree. Over several years, the disease progresses upward through the tree. Eventually, the symmetry and aesthetics of the tree are ruined and the tree is removed. (Examine the branch near the main trunk to see if there is a white crust forming on the bark.)

Cytospora canker is a fungus which causes the formation of cankers (open wounds) on branches. These cankers are small and difficult to see at first but they eventually grow to girdle and kill the branch. The fresh pitch (sap) which flows from the open wounds is an amber color but it eventually dries into a white, crusty coating.

Shaving the bark carefully between diseased and healthy tissue will reveal tiny, black fruiting bodies of the fungus. Spores ooze from the fruiting bodies during wet weather and may cause new infections if they land on nearby branches.

If you plant susceptible species, give the enough room so that, when mature, their foliage does not touch a neighboring tree's foliage.

Early detection and removal of infected branches may help control the spread of the disease. Look closely at other branches near the dead limb for early symptoms of infection such as the amber colored seepage or the white crust. If symptoms are discovered, these branches should be removed along with any dead limbs.

Infected branches cannot be saved and should be pruned back to the trunk. The diseased trimmings should disposed of away from the area since they are a primary source of spores which may cause new infections.

Trees stressed by lack of water, crowding or low fertility in the soil tend to be more susceptible to Cytospora canker. Keeping trees vigorous through fertilizing yearly and watering during periods of drought in the summer may help minimize the impact of the disease.

There is no chemical control available for Cytospora canker at this time.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

 
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