Can you give us your location? Also, do you know what kind of oak it is?

With a tree that size and well established, there is nothing you can do but wait and see what it does over the summer.

In my midwestern location, we had an extreme cold snap with extreme winds right before Christmas that lasted about 3 days. That caused some limb dieback on various trees in my area, especially those that have little tolerance for temps lower than my zone 6 norm.

You mentioned cicadas…I also live in an area that had a very heavy brood X infestation summer of 21. I had lots of limb die back that summer, a little more in 22, and even some more this spring. Every limb smaller than about 1/2 inch has a calloused over split line on the underside..:and I’m convinced trees are still shedding some of those heavily damaged thin limbs.

So if it puts on new growth this summer, and there is no more limb die back…then it may simply be a combo of things causing the tree to get rid of damage and heal itself.

I am in Cecil County, MD. North Eastern MD at the top of the Chesapeake Bay.

Just found a bunch of lichens on it tonight and that there is a bunch of sap on many of the limbs that wasn't there before last year and wasn't there a few weeks ago.

Not sure exactly the type of oak...many a pin oak?

It doesn't look good at all. Very severe cicada damage could do that. One would hope a tree could recover from that -- my trees had some to fairly bad damage, but nothing that bad.

We just paid a certified arborist $75 to assess a huge tree in our front yard. Call one in your area