The fungus is windborne and can increase during periods of heavy dew. Remove and destroy diseased foliage and canes during the growing season and follow a rigorous fungicide program. Spray applications should be made every 7-10 days. Spray thoroughly to completely cover all plant surfaces. Follow all directions and precautions provided by the manufacturer on the label.
Cankers frequently start at wounds or where a young shoot comes out of a cane.
These dead areas enlarge until they surround the cane and kill all growth above the canker or elongate until they reach the crown of the plant and kill the entire plant. Canker-affected canes should be pruned back to healthy tissue. The fungicide spray program for black spot will also help control canker, especially applications immediately after pruning in the spring. Make pruning cuts clean and just above a bud. The fungus often enters new shoots killed by early fall or late spring freezes.