A Technical Report from The Bartlett Tree Research Laboratories
Cytospora (Valsa) canker is the most destructive disease of spruce, and is most common on Colorado blue spruce and Norway spruce. This stem and branch disease is most common on Colorado blue spruce and Norway spruce but will also infect other spruce species. As the disease progresses from lower to higher branches, affected trees become unsightly and lose their ornamental or screening value. Cytospora canker is most common in dense plantings and on trees over fifteen years old, but it occasionally affects younger trees as well.