03 Feb 2020
February 3, 2020

How to identify Oak Wilt

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Oak wilt is a destructive disease that affects many types of oak trees. It is a very serious disease and is responsible for thousands of oak tree deaths in the United States each year.

Oak wilt is caused by a fungus called ceratocystis fagacearum. The fungus moves from tree to tree in 2 ways: underground through root grafts or above ground through insects.

New infections can occur in trees when the fungus is carried from an infected tree to a fresh wound on a healthy tree. Fresh wounds usually leak sap, which attracts beetles that can move the fungus to healthy trees.

Oak wilt is identified in the red oak family by leaf discoloration and wilting. Usually the initial discoloring symptom is located in the upper portion of the tree during the mid summer months. After the color changes the leaves begin to wilt from the top down. Leaf veins will stop progressing discoloration in some leaves. Occasionally, entire upper portion of the leaf could show bronze discoloration.

In the white oak family the disease moves slower, usually 1 branch at a time over a period of many years. Discoloration in the leaves normally proceeds from the margins to the base, and is occasionally interrupted the leaf veins.

To prevent spreading the disease, avoid pruning oaks during the spring and summer months. Also, prevent construction damage to trees during all times of the year. Fungicides have been developed that may be effective in preventing oak wilt when injected into oak trees. Contact The Tree Doctor at 515-333-TREE(8733) with any questions about treatment or identification.