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Help identifying white oak disease #425490

Asked September 06, 2017, 2:45 PM EDT

I'm trying to determine what is killing this  white oak in our park.  I'm concerned because the whole park is filled with mature oak trees and that is a big part of the park's draw.  My fear is that its oak wilt.  On the last picture there is a wound to the root system by one of our city mowers.  Could that be the cause?  It gone from a healthy looking oak at the beginning of July to this in September.

Benton County Minnesota

Expert Response

White oaks are considered resistant to oak wilt. The more likely disease of white oaks is oak anthracnose. I cannot see a close up of leaves so can't compare that symptom or determine the type of oak. And I cannot tell from the picture whether the defoliation started at the bottom or top of the tree so I can't compare that symptom either. The injury to the root system likely stressed the tree and accelerated the disease process although I don't know the extent of the injury. If it is oak anthracnose, trees usually recover. There are things that can be done to help recovery as described in the following links. https://www.extension.umn.edu/environment/trees-woodlands/oak-wilt-or-anthracnose/ .And also is the following gives an overview of oak diseases: http://www.missouribotanicalgarden.org/Portals/0/Gardening/Gardening%20Help/Visual%20Guides/Oak%20Problems.pdf
MaryKay, Master Gardener, Tree Care Advisor Replied September 06, 2017, 5:53 PM EDT
I took some pictures of leaves.  I also met with a DNR forestry representative and he is thinking its BOB.  Burr oak blight?
The Question Asker Replied September 07, 2017, 11:49 AM EDT
With the better pictures I can see that you have a burr oak which has ridges on the bark and not a white oak which has smoother gray bark. It appears that the tree canopy is okay but the lower leaves are curling and brown on the edges. And they are brown across the veins which is characteristic of BOB. So I agree with the DNR rep. The following links will give additional information. There is also a link to the plant disease clinic that can test and confirm if this is BOB. 1. http://www.myminnesotawoods.umn.edu/2010/09/bur-oak-blight-bob-in-minnesota/ 2. http://blog-yard-garden-news.extension.umn.edu/2016/08/a-bad-year-for-burr-oak-blight.html 3. https://pdc.umn.edu/
MaryKay, Master Gardener, Tree Care Advisor Replied September 07, 2017, 2:35 PM EDT

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