Michelle Grabowski, UMN Extension Educator
In 2010 a new disease of Bur Oaks was identified in Minnesota. Bur Oak Blight, also known as BOB, is caused by a new, and yet unnamed species of the fungus Tubakia sp. It has been identified in Ramsey, Hennepin, Sherburne, Mille Lacs, Washington and Anoka counties in Minnesota. Gardeners should be on the look out for Bur oak trees with browning leaf veins and brown wedge shaped lesions on leaves. Symptoms typically appear in the lower canopy and progress upwards each year. Leaf blight symptoms generally appear in July and August. If you suspect a bur oak is infected with Bur Oak Blight call the Minnesota Department of Agriculture Arrest a Pest Hotline: 651-201-6684 (metro) or 1-800-545-6684 (Greater Minnesota).