The City of Eden Prairie is issuing a warning today to residents about the confusion between two tree diseases. Recently the City received several calls from residents who have been told by private tree companies that their trees are infected with Oak Wilt, and need to be cut down. Employees from the City's Forestry Division have investigated several of these complaints only to discover that what was being identified as Oak Wilt was actually a less serious tree leaf fungus called Oak Anthracnose.
A loyal reader also sent me this link from the University of Minnesota Extension about oak wilt:
http://www.extension.umn.edu/distribution/naturalresources/DD3174.html
It is important that residents be aware of the difference between these two tree diseases in order to prevent unnecessary removal of valuable trees. Oak Wilt is a vascular tree disease that blocks water entering the tree from the roots from getting to the trees leaves. The tree leaves then begin to discolor, wilt and eventually the tree dies. Oak Anthracnose, on the other hand, is a leaf fungus that flourishes in cool, wet conditions. Trees infected with Oak Anthracnose will develop brown blotches on their leaves, some of these leaves wither and die.
Although the look of both tree infections may be similar, wilting and dying leaves, there are 
several important differences between the two diseases: Oak Wilt is a deadly disease and trees infected with it should be properly removed to prevent further spread of the disease. On the other hand, Oak Anthracnose is not deadly and trees infected with this fungus will eventually recover, these trees should NOT be cut down!
Oak Anthracnose most often affects white oak trees, whereas Oak Wilt mostly affects trees in the red oak species group. To the right is a map showing areas of the country that are suffering from Oak Wilt problems. To tell the difference between trees in the white oak species group and red oak species group simply look at the leaves. If the tree has leaves that are round on the edges then the tree is in the white oak species group. If the leaves are pointed on the edges then the tree is in the red oak species group. Oak Anthracnose produces irregular spots or blotches randomly over the leaf.
Additionally, leaves may be curled or deformed along the outer margins of new growth. However, when leaves are affected by Oak Wilt, browning occurs on the outer edges of the leaves, leaving the center vein green. Both diseases may cause scattered premature leaf drop. Symptoms of Oak Anthracnose are typically most severe on the lower, inside branches of the tree where humidity levels are higher. Conversely, Oak Wilt typically affects the higher branches first and then moves towards the center of the tree. Although Oak Anthracnose may be aesthetically displeasing, it does not cause permanent damage to trees and infected trees do not need to be cut down.
If City residents are unsure whether their tree suffers from Oak Anthracnose or Oak Wilt, they can have a member of the Forestry Department of the City of Eden Prairie come out and evaluate the tree free of charge by calling Jeff Cordes (952) 949-8463, Parks & Recreation at (952) 949-8442. Or by logging on to the Eden Prairie Forestry page. If you would like more information on the symptoms of Oak Anthracnose or Oak Wilt you can visit the University of Minnesota’s College of Natural Resources. Please, please, please, don't cut down your Oak tree because somebody told you that it has Oak Wilt without first getting a second opinion on its condition. Call us. The City will help you with this.
