Is It Oak Wilt, Or Not?

Suspect Oak Wilt in NW Ohio - Lucas County
Photo Credit Amy Stone

From Amy Stone, OSU Extension, Lucas County

Oak wilt is a very serious and often deadly disease of oaks, specifically the oaks in the red or black oak group. The actual pathogen (Bretziella fagacearum) that causes the disease has been known to be in Ohio for many decades. Some years, it appears to be worse than others. Oak wilt is not like the emerald ash borer that spreads rapidly, almost like a tidal wave moving in one direction. Oak wilt builds in a way that it can radiate out to other like trees, but advances at a slower pace, but even then, can cause tree death in a single season, and often in a matter of weeks. When not managed it can continue to spread or move-out across an oak-dominated landscape, park, or woodlot as pictured below.

The fungus invades the sapwood or the water-conducting tissues of the tree. In addition to its actual presence in the tree, it also triggers a defense reaction by the tree to stop the fungal spread. This action interferes with water uptake from the tree roots upwards to branches and ultimately leaves in the canopy. The result is wilting. Leaves turn brown from the tips, inward to the base of the leaf that attached to the branch. It has been described that this transition on the leaf looks like if you dipped it partially in milk chocolate. Continue reading