Cytospora Canker in Blue Spruce

Colorado blue spruce is a popular tree for home landscaping. When healthy, they are beautifulevergreen trees. However, the home landscape can be a hostile environment to these trees andmake them more susceptible to fungal diseases. One of the most common is cytospora canker. Learnwhat 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 sprucevarieties. The fungus tends to attack older trees and trees stressed by poor environmentalconditions. This fungus rarely kills trees but does often make them so unsightly that they are nolonger desirable as ornamental trees in the landscape.

Cytospora starts on the lowest branches of thetree and spreads upward. The first noticeablesymptom is a dying lower branch with brownneedles. Cankers appear at the base of thesedying branches near the trunk. Resin or pitch willflow heavily from these areas and when dry,appear as very visible white patches on the barkof the tree. If there are dying needles and noresin, it's possible the tree is infected by anothercommon fungal disease called Rhizospaera needlecast.

Controlling Cytospora Canker on Blue Spruce

There are no chemical controls for treating spruce trees with cytospora canker. Once a tree showsdie back from cytospora, the only option is to prune out the infected branches. Improving thegrowing 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 whenit's wet. Clean pruning tools with rubbing alcohol or a 10% bleach solution before and after pruningto lessen the chance of spreading spores to other trees. Prune branches back to the base of the limbwithout cutting into the trunk of the tree. Jagged edges are more easily infected so make smoothcuts 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 canpreserve 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 cankerstarts, 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.