What are the White Patches on my Oak?
What are the White Patches on my Oak?
What are the white patches on my Oak? The presence of white patches on your oak tree could be a result of a fungal infection known as smooth patch. This particular infection affects the bark of various oak tree species. While there are several fungi that can cause smooth patches, the most common one is Aleurodiscus oakesii. Initially, this fungus was identified as Corticium oakesii in 1873. Smooth patch is a saprophytic fungus that thrives by colonizing and decomposing the dead outer layers of bark on living trees. It is also commonly referred to as white patch, smooth bark, bark patch, or bark rot. The infection is localized to the outer bark, leading to its shedding and the formation of smooth, depressed areas.
The smooth, light-gray depressions are usually irregular in shape and size, ranging from a few inches to more than a foot across. Smaller areas may merge to become larger patches. Infection can occur at any time during the growing season. Symptoms are most noticeable on the lower trunk of the tree but can also occur on larger branches. Small patches may slowly expand over time, merging to form smooth grayish areas that are several feet in length. Depressed areas appear to advance more rapidly in a vertical direction than radially around the trunk.
The presence of these formations might be confused with signs of wood decay fungi, but they do not result in cankers or internal decay. Smooth patch is most frequently associated with trees in the white oak group; however, it can also occasionally be found on birch, ash, willow, pecan, hickory, and sweet gum. Similar symptoms are caused by related fungi in various other hardwood and conifer species. As the patch fungi only infiltrates the nonliving, outer bark tissues, this condition does not harm the tree and has no long-term impact on either tree health or structure. Smooth patch may indirectly affect the tree’s health by reducing bark thickness, thereby decreasing protection against drying out and physical damage. No specific measures are recommended for controlling smooth patch, other than promoting healthy tree growth through appropriate watering and fertilization. It is also important to avoid injuring the trunk and branches, as these are common sites for fungal or bacterial infection that can result in internal wood decay.
The fungus spreads mainly through wind and water splashes from rain or overhead irrigation. The symptoms of this disease are typically subtle, making them easy to miss for the casual observer. Smooth patches can be observed on oak trees in urban as well as forested regions. Once the disease is recognized, individuals quickly realize its prevalence.
Contact Johnson Ops Tree Care for an assessment of your landscape at 608 526-6297.