The blue spruce tree is a colorful, decorative conifer tree which is relatively disease and pest free, excepting two pernicious diseases which can quickly kill a blue spruce if not identified and treated. As the blue spruce tree produces lovely year round colorful dense foliage that makes an excellent accent, shade, or windbreak tree, it is a popular choice for many home gardeners. As is often the case, home gardeners may be mystified when their vibrant blue spruce suddenly begins to decline. In most cases, either cystospora canker or rhizosphaera needle cast is the culprit. Learn tips from expert horticulturists about how to identify and treat these diseases.
Rhizosphaera needle cast is a fungal ailment that affects the needle like foliage of the blue spruce tree. It is by far the most common of all blue spruce diseases. The tree will first show symptoms on the lower branches, as needles turn first a purple color, then brown, and then begin to fall from the branches. The tree can begin to appear as though it is slowly dying from the trunk on up. Patches of brown, needle bare branches can also begin to appear higher up on the tree. Treating rhizosphaera needle cast involves removal of the affected areas and spraying with a fungal spray that is specifically formulated for rhizosphaera needle cast.
Cystospora canker is the other major fungal ailment that affects the blue spruce tree. Here, the branches will begin to die back, and the fungus will show its presence with a sticky white sap that appears as the foliage dies away. As the fungus enters through wounds, careful pruning and maintenance can help reduce the risk. If cystospora canker develops, the best treatment is to remove the affected branches and at least six inches around any affected areas. Also spray with a fungicide spray.