Canker diseases result in the formation of distinct, sunken lesions on the bark of woody plants. Cankers restrict water and nutrient movement and may ultimately lead to branch dieback and tree death. Botryosphaeria canker is a serious canker disease, occurring primarily on Rocky mountain junipers. Botryosphaeria canker , caused by the fungus Botryosphaeria stevensii , has been reported from the Great Plains region but is probably more widely distributed in the United States.
Affected junipers develop elongated, flattened, often resinous cankers.
These cankers may occur anywhere on woody stems but are commonly located near branch crotches in the interior portion of the tree crown. Cankers are often difficult to see, and it is often necessary to cut the dead branch off and carefully scrape away the outer bark to expose the chocolate brown, dead tissue in the canker. Surrounding healthy tissue will be pearl white. Small, black fruit bodies of the fungus also develop in the canker, but these may be partially hidden by thin pieces of dead bark. Occasionally, girdling stem cankers cause rapid death of the top third to one-half of the tree crown.