Oak wilt is a fungal disease that infects the vascular tissue of oak trees. As the fungus infects the tree, the tree defends itself by producing defense compounds. These compounds plug the water-conducting tissue causing the tree to wilt and eventually die.

Red Oaks are more susceptible to wilt and once infected can die within weeks. White oaks are not as susceptible and in some cases can take years before they die. To identify trees infected with oak wilt, watch for wilting leaves in the upper canopy. Wilting leaves may develop yellow margins, while the interior portion of the leaf remains green. As the tree continues to wilt, leaves turn brown and fall from the tree.

The oak wilt fungus spreads in two ways. New infection centers are started when a beetle (known as the picnic beetle) lands on a fresh oak wound generally during the months of April, May, or June. The fungus may then be inadvertently transferred into the tree and a new infection center is started. Once a tree becomes infected with oak wilt, the disease can spread to adjacent oaks through root graphs.

The Chisago Soil and Water Conservation District has a forester that can assist with oak wilt questions. Cost share dollars are available to assist in treating infected oak wilt centers. Check the web page at www.chisagoswcd.org or call (651) 674-2333 for more information regarding the Chisago County oak wilt suppression program.