Cytospora canker, caused by the fungus Cytospora kunzei (also known as Valsa kunzei var. Cytospora is a canker disease that starts in lower branches and spreads upwards. Another key characteristic of needl… For best effectiveness, fungicides should be applied when the emerging needles are half elongated (1/2 to 2 inches in length). piceae), is the most prevalent and destructive fungal disease of Norway and Colorado blue spruce. At least 2 years of treatment will be necessary to allow trees to begin to recover their full complement of needles. Susceptibility varies widely among species, but generally trees under stress or growing outside their natural range are more prone to the disease. A common fungal disease, Cytospora canker generally affects older blue spruce trees but may also infect Norway spruce. Two needle cast diseases occur in North Dakota: Rhizosphaera needle cast and Stigmina needle cast. Similarities and differences between the two diseases exist. Cytospora canker rarely affect… But, some blue spruce will be much more susceptible to this needle disease throughout their lives, regardless of the weather, and may need continued treatment to maintain a … A: The indication in the photograph (shown here) are classic symptoms of a common foliar disease called Rhizosphaera Needle Cast, which routinely affects Colorado Blue Spruce … Needle cast diseases can be effectively controlled with fungicides containing chlorothalonil. The classic symptoms of needle cast include brownish purple discoloration and eventual death of older needles, while current-year needles show no symptoms (Figure 1). There is no known cure for Cytospora canker fungus, so fungicide treatments are not recommended. Occasionally, Cytospora canker is found on Douglas-fir, hemlock, and larch. Protecting new growth as it emerges is very important. Symptoms of both needle cast diseases look similar to each other. 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