Colorado blue spruce is a popular tree for home landscaping. When healthy, they are beautiful evergreen trees. However, the home landscape can be a hostile environment to these trees and make them more susceptible to fungal diseases. One of the most common is cytospora canker. Learn what to look for and how to best combat this infection.
Identifying Cytospora Canker in Blue Spruce
Cytospora canker is a fungal disease that is very common in blue spruce as well as other spruce varieties. The fungus tends to attack older trees and trees stressed by poor environmental conditions. This fungus rarely kills trees but does often make them so unsightly that they are no longer desirable as ornamental trees in the landscape.
Cytospora starts on the lowest branches of the tree and spreads upward. The first noticeable symptom is a dying lower branch with brown needles. Cankers appear at the base of these dying branches near the trunk. Resin or pitch will flow heavily from these areas and when dry, appear as very visible white patches on the bark of the tree. If there are dying needles and no resin, it’s possible the tree is infected by another common fungal disease called Rhizospaera needle cast.
Controlling Cytospora Canker on Blue Spruce
There are no chemical controls for treating spruce trees with cytospora canker. Once a tree shows die back from cytospora, the only option is to prune out the infected branches. Improving the growing environment and general health of the tree also helps to control the spread of the fungus.
Because the fungus spreads by spores which grow during wet weather, avoid pruning the tree when it’s wet. Clean pruning tools with rubbing alcohol or a 10% bleach solution before and after pruning to lessen the chance of spreading spores to other trees. Prune branches back to the base of the limb without cutting into the trunk of the tree. Jagged edges are more easily infected so make smooth cuts when removing branches. Destroy infected branches.
Improving the overall health and environment of the tree can also reduce the incidence of infection. Water trees during periods of drought and fertilize regularly. Mulching around the base of trees can preserve moisture and prevent tree injury from mowers or trimmers.
While cytospora canker can ruin the aesthetics of a blue spruce, most often it will not kill the tree. Maintaining the health of the tree will help prevent fungal infection. Once the cytospora canker starts, remove the diseased branches to prevent further infection.
Sources:
Nameth, S. , C.W. Ellet and J. Charfield. Cytospora Canker of Spruce. Extension FactSheet HYG-3033-96, Ohio State University Extension. http://ohioline.osu.edu/hyg-fact/3000/3033.html
Clement, D.L, M.K. Malinoski and E.M Dutky. Cytospora Canker of Spruce. Home & Garden Mimeo # HG 400, Maryland Cooperative Extension. http://www.hgic.umd.edu/_media/documents/hg400_000.pdf.
Paula Lovgren - Paula is a freelance writer, gardener, garden designer and mother to two children and three cats. She has previously worked as a marketing ...
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