Cytospora canker (Leucostoma kunzei Sacc.) is the most serious of spruce-conifer cankers. It Affects mostly ornamental Colorado spruce trees growing out of their natural range. All other spruce trees, particularly Norway spruce, as well as white pine and other conifers can also be affected. The disease Rarely kills but detracts from the tree's natural appearance and asthesics.
The canker affects bottom branches or random ones throughout the canopy. Its onset is often triggered by environmental stresses such as excessive drought, insects, bark damage, or contamination from tools.
Browning of needles and dying branches usually occur from the bottom up. Patches or the oozing of white (and sometimes blue) sap along with small black dots on the bark be a sign of cytospora Canker. The disease can otherwise be hard to detect due to a lack of outward visual signs. Older trees are more commonly attacked and entire trees may be killed if the trunk becomes girdled by the fungus.
Cytospora canker is mainly spread by rain, wind, insects and tools. The best control measure is to prune out diseased branches back to healthy wood and avoid pruning in wet conditions. Ovoid injuring the bark to prevent further spread.
Proper watering will enhance the tree's natural defenses as drought leading to weakened health is a major cause of the disease. Infected and declining trees become more vulnerable to attacks from boring beetles, mites, scale, and other insects. Besides good cultural practices, there are no recommended sprays available to control cytospora canker.
Natural Resources Canada. (2015). Canker disease of spruce. Retrieved from https://tidcf.nrcan.gc.ca/en/diseases/factsheet/263
University of Illinois Extension. (n.d.). Cytospora Canker of Spruce. Retrieved from https://web.extension.illinois.edu/focus/index.cfm?problem=cytospora-canker-of-spruce
University of Maryland Extension. (n.d.). Cytospora Canker of Spruce. Retrieved from https://extension.umd.edu/hgic/topics/cytospora-canker-spruce
University of Minnesota Extension. (2018). Cytospora canker. Retrieved from https://extension.umn.edu/plant-diseases/cytospora-canker