Cronartium ribicola fungus was introduced to North America in diseased planting stock in the early 20th century. In later stages of infection, tree bark appears yellow or bronze.
Dead branches are reddish brown.
These cankers can persist for several years before a branch is killed. Older cankers often exude resin. In early spring, orange-yellow, powdery masses of spores are produced on cankers. Cankers may progress along the branch to the main stem of the tree causing symptoms similar to those on branches. White pine blisher rust has caused more damage and costs more to control that any other conifer disease.