Sunscald of Woody Plants

Overview

Sunscald also called southwest injury occurs in late winter and early spring on the southwest side of thin bark trees. The direct sun or reflected sunlight from snow or light-colored structures heats tree bark during the day. The tissues become active and break dormancy. With freezing nighttime temperatures, the active tissues are killed. The bark area involved shows an elongated canker that appears discolored and sunken. Cracking and peeling of the bark may follow. The damage may not show until the next spring or summer when new growth occurs. Further problems from insect and disease entry at the damaged site may affect the tree. Any loose bark can be removed from the split using a sterilized knife or pruner. The tree will normally heal itself.

Young, thin bark trees are most susceptible, particularly newly planted trees. Older trees of the same species develop thicker bark and established root systems.

These species are at risk: beech, dogwood, honey locust, linden, mountain ash, sugar maple, cottonwood, and fruit trees.

Integrated Pest Management Strategies

1. Wrap the bark of young trees with commercial tree wrap. Be sure to remove the wrap in spring. If left in place, it attracts insects and diseases. Over time it can also girdle the trunk.

2. Paint tree trunks with white latex paint to reflect the sunlight. The light color will reflect light and slowly warm up and delay the bark coming out of dormancy.

3. Prune with care. Avoid heavy pruning of older trees that would expose limbs and trunks that have been shaded to direct sunlight. Gradually thin out limbs over several years.

4. Provide shade for the tree with temporary fencing.

5. Provide good care. Water adequately (1 inch per week or saturate to a depth of 12 to 18 inches). Mulch the entire root zone to conserve moisture.

Organic Strategies

All of the recommended IPM strategies are strictly organic approaches.