Cytospora Canker of Spruce
Spruce trees in this area can exhibit a number of problems, many of which are tied to the environment. Cytospora canker, which is caused by a fungus, is a case in point. This disease primarily affects blue spruce and Englemann spruce, but it may also occur on red and Norway spruce, Douglas fir, and eastern white pine. Although the disease may not kill the tree, it can result in significant branch dieback, and seriously reduce the aesthetic quality of the tree.
The symptoms first appear on the lower part of the tree. Individual branches appear off-color, and the inner needles turn brown or purple and then drop from the branches. On close examination, there is a discolored area of bark on the branch, usually near where the branch joins the main trunk. This is the canker. The canker is commonly covered with a white pitch mass, which, if abundant, can drip onto nearby branches. The wood beneath the cankered bark is saturated with resin and is dark blue or brown. The presence of the white pitch and the discoloration of the wood beneath the cankered bark are diagnostic of the disease. A canker eventually girdles the branch and kills it.
The fungus over-winters in the margins of active cankers, from which it can spread to adjacent branches until all the lower branches are killed.
If Cytospora canker is present, remove cankerous branches at the junction with the main stem. Disinfect pruning tools with rubbing alcohol or a 10 percent bleach solution. Fungicide applications will not control this disease. The real key to preventing Cytospora canker is to know that spruces are not native to this area. They are native to cooler climates with consistently moist soils, and are shallow-rooted. So, spruces will be weakened by periods of high heat and drought. If you do plant a spruce, plant it on well-drained, deep soils, knowing that, during periods of drought, you must provide adequate moisture. Never let the top 6 inches of soil dry out. Monitor insects that could also weaken the tree and make it more susceptible to environmental stress. Do not use herbicides or cultivate in the area near the trees. Use an organic mulch to keep the soil as cool and as moist as possible during the summer.
Thinking of planting a spruce? Think twice. Spruces do not like hot, dry, polluted conditions. Consider planting a tree more adaptable to this area.