Oak wilt is a fungal disease that can affect all types of oaks. Red oaks are particularly susceptible and can die very quickly once infected with the fungus. 

Help prevent the spread of oak wilt by not pruning or removing oaks from April-July. This is the highest risk time for the fungus to spread. 

The drought conditions in recent years have been stressful for trees. This has led to an increase in other problems that look similar to oak wilt, such as damage from twolined chestnut borer. Twolined chestnut borer is a native beetle that often attacks stressed oaks. Help trees during dry stretches with regular watering. 

Learn more about oak wilt:

• University of Minnesota Extension
• Minnesota Department of Natural Resources
• Common disease guide

If you have an elm tree, it may be at risk for Dutch elm disease. The first symptom of Dutch elm disease is branches of yellowing leaves near the top of the tree. If you notice this early in the summer, call a certified arborist immediately.

• University of Minnesota Extension
• Dutch elm disease-resistant elm trees

Bur oak blight is a newer disease that is becoming more common. It will affect bur oak trees for several seasons, eventually leading to death. The first symptom is triangle- or wedge-shaped brown areas on leaves. There is currently no treatment available for bur oak blight. However, a certified arborist can help create a management plan.

• Minnesota Department of Natural Resources

See the page on emerald ash borer

Additional resources:

• University of Minnesota Extension
• Minnesota Department of Natural Resources
• How to identify an ash tree

• University of Minnesota Extension’s plant diagnosis guide
• Helping trees to manage stress