Cytospora Canker of Spruce particularly attacks blue spruce, in addition to Norway spruce, hemlock, red cedar, fir and white pine trees.
Infection by this fungal disease commonly starts in the lower limbs and gradually works up the tree limb by limb. Needles turn a dull yellowish-green then purple-brown. Soon, needles fall from the tree, leaving bare ends on the branches. Normal water movement to the needles beyond the infection is restricted, so the branches dry out and turn brown.
The cause of the canker is a fungus that primarily attacks trees that have been weakened by conditions such as drought, low fertility, mechanical injury, insect feeding or poor soil conditions. This is why cankers are typically found in trees that are more than 15 years old. The disease is most commonly spread by splashing rain, wind and insects.
There is no known cure for Cytospora canker, so fungicide treatments are not recommended. The most effective approach in managing this disease is to maintain the health and vitality of susceptible trees. Vigorous trees are less susceptible to Cytospora canker, and if infected will slow the progress of the disease. Trees should be fertilized proactively, rather than waiting until the disease is evident.
Supplemental watering is also important for landscape trees, particularly during periods of drought. Infected branches should be removed while sterilizing pruning tools between cuts. Avoid pruning during wet weather to reduce spread of disease.