Looks like it could be oak wilt. What does the tree look like, and have the leaves been falling from the tree? Do you know if there is oak wilt in your area?

~1/3 of canopy is brown and the tree is shedding. There is no known issue in the area that I know of. 2 Oaks in my yard. The other is shedding as well but the browning pattern on the leaf is not like this.

Can you call your local county extension? They probably keep stats on oak wilt incidences in the county. They might even come ck your tree out, in case you happen to be first case.

Thanks for the suggestion! Multiple arborists also scheduled to come out in the next few days.

do keep us updated.. please ... thx.. ken

There are many stories in here about arborists who use the title VERY loosely. You might casually want to ask about their credentials; if nothing else, to see who is straightforward and who is BSing. Good luck.

Thanks. I have ~3 different guys coming out. Hopefully there will be consensus. Pinged county folks via email and am being bounced to the right place, hopefully.

Per our Forestry Dept, Oak Wilt is not a issue here. Bacterial Leaf Scorch is the likely culprit. Leaf browning pattern looks similar. Treatment options look similar...removal.