Written by John Sepulveda, Certified Arborist WI-1454A
Cytospora canker is a fungal disease caused by Leucocytospora kunzei. It commonly attacks Colorado blue spruce and to a lesser extent Norway spruce, balsam fir, and Douglas fir. Trees older than 15 years old are most often affected, but younger trees can also be infected if they have other stressors.
Signs of Cytospora Canker
As with other fungal diseases that affect blue spruce, the lower branches are often the first to show signs of the disease. The needles on the tree will turn a purplish hue, then brown and will die. Needles do not always fall off immediately but they can be a source of spores.
The namesake of this disease, the canker, is not always visible due to a lack of color change but it is often found at the base of branches and covered in a layer of sap and resin. These cankers girdle the branch and cause it to die and fall off. The sap that oozes out of the branches is usually blueish-white in color and visible on infected branches. Trees that have this disease are also at risk from other pests which can accelerate their decline and cause death.
How Cytospora Canker is Managed
Foliar applications of fungicide have not proven effective in curbing Cytospora canker. Trees that are stressed are more prone to this disease, so improving overall tree health is essential. To manage the canker, Hoppe often recommends fertilization treatments and the use of growth regulators along with pruning. Maintaining good airflow in the canopy is important because too much water and dampness can lead to the fungus spreading more easily. Diseased branches should be pruned off immediately and destroyed. This should only occur in dry weather and tools used should be disinfected between cuts to prevent spreading to healthy tissue. Bark damage should be minimized because open wounds are a point of entrance for the fungus.
Planting new blue spruce trees is not recommended because of the canker and other fungal diseases they are susceptible to, such as Rhizosphaera needle cast. If new spruces are planted they should be spaced well apart and planted in well-drained soil.
If you think your Colorado blue spruce trees might be showing signs of Cytospora canker or you are not sure why they look unhealthy, give us a call. One of our certified arborists will come walk your yard and inspect your trees. We can make the proper diagnosis and recommend a plan for healthy trees in your landscape.