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Diseases in Oak Trees

Oak Processionary with hairs walking on a oak-tree image by Ivonne Wierink from

Oak trees are popular deciduous trees that have lobed leaves and produce acorns. There are more than 400 different species of oak trees, according to These trees are prone to several diseases so it’s important to recognize signs of a problem before an oak trees weakens or dies. Common symptoms of an oak tree disease include spotted or discolored foliage, dying branches or foliage, wet patches on trunks, thinning canopies and white coatings.

Anthracnose Disease

Anthracnose disease includes a group of fungus-related diseases attacking shade trees. Symptoms of the fungus on an oak tree are small brown spots or large light brown splotches forming along a leaf’s veins, giving leaves a scorched appearance. It causes leaves to defoliate and die prematurely, as well as kills buds and twigs. Although it’s not usually fatal, repeated attacks of anthracnose can result in a tree having stunted growth.

Oak Wilt

Oak wilt is the most fatal of all oak tree diseases. It’s a fungal infection attacking an oak tree’s vascular system which causes an obstruction of the flow of essential nutrients and water. Common signs of this fungus are leaves losing color and falling prematurely. Unfortunately, there isn’t a cure for oak wilt, but other nearby trees can be saved by killing an infected tree.

Oak Tatter

Oak tatter is a disease that typically attacks in spring and mostly affects the white oak group such as bur, white and swamp oak trees. The disease involves an oak tree’s leaves becoming tattered or lacy. In most cases it destroys leaf tissue. While healthier trees are able to survive the disease, other weaker trees are damaged by it. This disease is the result of unfavorable environmental circumstances such as low temperatures or strong winds that damage developing buds. In time a tree will recover so spraying is not necessary.

Gypsy Moth

Gypsy moth is a disease caused by caterpillars that begin emerging in early spring and continue to damage oak trees through mid-May. While young caterpillars are brown or black, older ones develop bumps on their backs with black course hairs. The disease can cause injuries ranging from minor damage to almost defoliating a tree. Continual attacks can weaken a tree and also make it susceptible to other diseases and insects.


Wetwood is a major reason for the American red oak lumber industry losing value, according to the Tree Search website. The disease causes foul smells from sap seeping from a tree's trunk. Infected wood is often discolored, appearing water soaked, giving the disease its name of wetwood. Sap may continue oozing out of a tree trunk for weeks or even months, although it generally stops without treating the problem. Wetwood can be caused by drought, hot temperatures or other stresses to a tree.

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