Adding mulch around trees increases overall health in many ways, including reducing competition from turfgrass. Plant trees in a good site, one that is well-drained and allows unrestricted growth as the tree matures. Brown needles can be observed on killed branches, but they eventually fall off, leaving bare branches.Īs with many diseases, the best control for Cytospora canker is prevention. Over time, the fungus encircles or girdles branches, causing death. The Cytospora fungus gains entrance into branches or twigs of trees through wounds or branch stubs. Infected trees produce this resinous sap in response to the infection by the canker fungus. A close look at the dead branches usually reveals the presence of sticky white sap. Spruce trees infected with the Cytospora canker fungus typically show scattered branch dieback, often starting on the lower branches. The Cytospora canker fungus may attack many different species of hardwood trees, conifers, and shrubs. Trees weakened by environmental stresses, such as drought, freeze injury, or high temperatures, also are more susceptible to canker diseases. Cytospora canker is observed most often on older trees, especially those that are planted in poor sites. The most common canker disease observed in the Iowa State University Plant Disease Clinic is Cytospora canker on blue spruce. When we see diseases in blue spruce, which is not often, it usually is one of two different types-Cytospora Canker and Rhizospharea Needle Cast. In addition to being a beautiful tree that maintains color year round, these trees make an excellent wind break and for the most part grow quite well here. Blue spruces are a favorite conifer of Iowans and several reasons.
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