The fungus, Cytospora kunzei , more properly identified as Leucostoma kunzei causes this canker disease. It is also known as Valsa canker. Cytospora can infect branches through wounds and branch stubs, but does not actively develop a canker unless the tree is stressed by drought. Most cankers on spruce remain on the branches, but Norway spruce is found with trunk cankers. Cankered areas on branches or trunk produce spores in small fungus fruiting bodies that are exuded during periods of wet weather.
Rain splashes the spores onto nearby branches and infections occur through wounds.
The most noticeable symptoms are the browning and eventual death of lower branches of older trees. The disease progresses upward at a slow rate until the entire tree may be infected. Infrequently, branches high in the tree may be the first to turn brown and die. Dead, brown needles persist through much of the growing season and drop during the winter, leaving bare twigs and branches. Another conspicuous symptom is the presence of large amounts of bluish-white pitch or resin on the bark of dead or dying branches.