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Sun-scald canker on ornamentals

Trunk cankers on various ornamental hardwood trees and thin barked saplings are reported from all parts of Region I. Silver maples, willows, cherries and apples are affected. Sun-scald occurs during both winter and summer when portions of the cambium are killed due to temperature stresses especially on trees with dark, thin bark.

Summer sun-scald is heat injury to the exposed bark during the summer months. A canker forms around the damaged area. The wound can lead to decay eventually creating a permanent defect. Winter sun-scald is injury from rapid changes in bark temps during cold, sunny winter days. Exposed darker bark becomes much warmer on the sunny side than the air during this period, but cools very rapidly after sunset. The temperature changes can result in bark injury that also results in canker formation.

Both summer and winter sun-scald injuries tend to occur on the south to southwest side of the tree. Trees are most susceptible when they are growing in the open, when stands are excessively thinned or when trees are moved from a shaded nursery to an exposed site. Crown die back is usually associated with these cankers.

Sun-scald can be prevented by wrapping the trunks with a commercial tree wrap, plastic tree guards or any other light colored material. The wrap will reflect the sum and keep the bark at a more constant temperature. Put the wrap on in the fall and remove it in the spring after the last frost. Newly planted trees should be wrapped for at least two winters and thin-barked species up to five or more winters.