- Cracks in bark
- Sunken areas in trunk
Sun scald, also called southwest injury can cause bark cracking, splitting of bark, sunken areas in trunk, etc. These conditions are typically seen on the south or west facing side of the tree, but can occur in other areas where light may have been reflected onto the tree from either snow or rocks. These cracks are typically invaded by diseases or insects due to a lack of defenses.This problem most commonly affects ashes, honey-locusts, flowering fruit trees, mountain-ash, maples, lindens and willows.
Sun scald is caused by a warming period in the midst of a cold season, similar to winter injury, but affecting the bark instead of the foliage. The heat of the sun causes the tree to break the dormant period; rapid cooling due to the loss of sunlight at night results in the cell death. The south or west-facing portion of the tree is usually the affected side as it is at a high exposure to the sun and receives the majority of the warming.
The best methods to limit sun exposure to the trunk are by wrapping the trunk loosely with tree wrap (up to the first branch) or by painting the trunk white. The painting method is rarely used in landscapes due to the permanent change in color, but is an effective technique in orchards. Also, planting in areas that are limited to southern sun can help prevent sun scald.
Pesticides are neither available nor recommended for managing this condition.