Cytospora canker can cause serious and unsightly damage to spruce trees. It mainly infects blue and Englemann spruce, but also attacks red spruce, white spruce, Norway spruce, Douglas fir and white pine trees. Cytospora canker is caused by the Leucostona kunzei fungus, which is also known as Cytospora kunzei. The fungus spores are spread from branch to branch and tree to tree by rain, wind, people and animals. Cytospora canker tends to infect trees 15 years or older, although it can affect trees at any age.
Cytospora canker begins attacking the bottom of a spruce tree and works its way up. The tree may exhibit discolored branches and needles die and fall off the tree. If visible, the canker itself looks like a discolored area of bark on a branch, usually near where the branch meets the tree trunk. Many times the canker is covered with a white, sticky sap. The wood underneath the bark is also discolored. The canker continues to spread around the diameter of the branch, eventually killing it. The fungus will spread to other branches of the tree, eventually killing those branches. When enough branches die, the tree will die.
Spruce trees that are planted in locations not suited to their needs are susceptible to cytospora canker. Trees that are exposed to dry, hot conditions or drought become stressed and are more likely to become diseased.
Cut away all infected branches as close to the tree trunk as possible. Do not cut branches if the tree is wet to avoid spreading the fungus to other branches. Disinfect all pruning tools with alcohol or bleach to prevent spreading the fungus further. There are no fungicides or chemicals available that kill cytospora canker.
According to Dennis Patton of the University of Missouri Extension and Kansas State University Research and Extension project, "spruces will be weakened by periods of high heat and drought." When planting a spruce tree, make sure the soil is well-drained and always moist. Place a deep layer of mulch around the tree to keep the roots cool and the soil moist during periods of high temperatures. Apply fertilizer to encourage strong, healthy growth.
Spruce trees prefer cool, moist climates and do not get cytospora canker when grown in their native habitat.
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