Cause: Dieback may be the result of decline (see page 15 for discussion of decline), canker fungi or winter injury. Examine dead branches to determine if a canker is present at the basal end of the dead portion of the branch. A canker in this position is usually swollen. If the dieback is not due to cankers and the plant otherwise is vigorously growing and healthy, then winter kill is a possible cause. Winter kill of branches is most common in trees and shrubs that are not well adapted to cold climates. About once every 10 years, an especially cold winter will descend on the north central states and will injure numerous trees and shrubs growing beyond their native range.

Control for dieback due to winter injury: Replace plants with cold-tolerant cultivars. Otherwise, prune out dead branches and revitalize the tree as described under "General decline and dieback."

Control for dieback due to fungal cankers: Refer to "Cankers" section of this bulletin.