Smooth Patch: An interesting bark condition on bur oaks

Mature bur oak trees have very thick bark with deep ridges. You can almost bury a pencil within the tree’s crevices. However, occasional trees have areas on the trunk that have sloughed off that outer thick bark, exposing a lighter inner smooth bark. Such a condition is called “smooth patch” and it is caused by infection with the fungus Aleurodiscus oaksii. According to University of Minnesota Forestry, the fungus does not attack living plant parts and no control is necessary.

An area on "smooth patch" on a large bur oak in Unit 10 savanna.
Most bur oak trees at PVC do not exhibit this condition.

This condition also occurs on white oaks.