Moment of absolute death - apopsis - with no hope of vascular recovery - generally happens in oaks that host wilt and the bud development from late summer throughout the Fall is the straw that breaks the proverbial camel's back.
The periphery twigs may look as though there are swelling buds, indicating next season's leaf - but take those sticks in hand and break them - brittle means dead, softer inner tissue may indicate dormancy. Move on down the limb and examine larger diameter tissue....more dry brittleness and continued death.
We've discovered that the demands of bud development pretty much seal the tree's fate if there is active systemic infection of vascular inhibiting fungal growth, which is wilt's operandi atipicum. Don't condem the entire tree however - there are documented cases of recovery. It's your call depending on the value and location of each specimen. It's now late Jan. - are you familiar with fruiting stimulation technique?
You have wilt, I'm banking a wager on it. 78 Texas Counties are reporting active progressing infection centers. What is important that advice offered by the State or agencies guided by the wisdom of A&M be taken with two aspirins and a sweatcloth of critique - their data is flawed and recommendations favor chemical peddlers who underwrite research objectives - well known in plant science circles.
Look towards the base of the main stem - excise tissue and examine closely - you'll know the difference between dead and pliable, base your removal decisions on that.
