
Smooth patch on lower trunk of a white oak tree
Key Points
- Smooth patch goes by other common names including white patch or bark patch.
- The most commonly affected oaks in Maryland are white oak, Q. alba, and post oak, Q. stellata.
- Smooth patch can be found on oaks in both urban and forested areas. White patch symptoms on trunks are commonly seen and are often used in a forest setting for identifying white oaks from other oak species.
- Symptoms are often noticed when looking for reasons why a white oak tree is declining in the landscape.
Symptoms and Causes of Smooth Patch
- The main symptom is sunken white-colored areas on trunk bark.
- The smooth patch fungus produces clusters of flattened cuplike spore-bearing structures on the bark surface.
- These structures are light gray or beige in color, are usually less than 1/2 inch in diameter, and are usually curled at the edges.
- Exfoliation of the bark results in smooth, grayish patches adjacent to the normally rough bark.
- It is caused by a superficial colonizing fungus, Aleurodiscus oakesii.
- Since the fungus invades only the nonliving, outer bark tissues, this colonization is not harmful to the tree and has no long-term affects on tree health.
Management
- Treatment is not necessary.
- Deeply water trees during drought and avoid wounding the trunk and branches of trees.
Additional Resource
Author, Dr. David L. Clement, Extension Specialist, Plant Pathology