Bur Oak Blight (BOB) is caused by a fungus named Tubakia iowensis. It is a leaf disease that attacks oak trees causing severe decline and death.
Bur oak trees of all sizes are at risk of bur oak blight. Other trees such as swamp white oaks have also been affected, although it is not as common.
Small, circular leaf spots are the most initial symptom of BOB. The disease eventually spreads to the leaf veins, discoloring them and forming small, black fruiting bodies that contain fungal spores. These spores are the primary source of infection, spreading through rain and wind. Leaves will eventually brown starting from the tips of the leaves, creating wedge-shaped necrosis. Trees may appear to have healthy foliage through the summer, but early fall will show signs of damage.
This disease is very difficult to manage. Bur oak blight may look serious but is not typically the primary pathogen responsible for tree decline. Bur oak blight is a stressor, therefore it can be managed by reducing tree stress. Techniques such as appropriate watering, mulching, and soil modification are recommended to boost tree health. A tree stressed by bur oak blight is susceptible to two-line chestnut borer and management for the borer should be considered as well. Consult with your local arborist for more information on protecting your trees.