Smooth patch is sometimes called bark patch or white patch. At least three saprophytic fungi cause this disease, but none are known to cause any major damage to the tree.    

Symptoms

The fungi break down the outer rough dead bark leaving a smoother light gray bark behind. Small patches often merge to form large patches. The smooth patch fungi will produce whitish looking fruiting structures under the right conditions.  

Life Cycle

The fungi survive on outer dead bark. Spores are spread by wind and water.  

Management

No control is recommended.