Can it be saved, or is it too late.

Trees can have various stages of EAB infection.  How do you know if it is too late to save it?
Trees need good Xylem flow from the roots to the leaves to bring the insecticide up .  If the branch no longer has leaves, it can not be saved.

For trees with a thinner leaf coverage, a good number to remember is 40%.  A tree can be 40% thinner from the ash border activity cutting off the xylem in the branches and still be saved.  My experience is if the leaves are thin and airy like the size of your fingers, that branch will not come back.
That might mean one branch, or the top 1/3 of the tree won’t come back with treatment, depending on infection. Remember, the Ash Borer starts at the top and kills the tree from top to bottom.
Photod below is a tree that was reduced by 40% in 2023.  WIth treatment that spring, the EAB was checked, and the tree fully recovered in 2024.  Notice the neighboring trees not treated are mostly dead, or ever already stumped.

The main take away is if you are in EAB zone, where it is with in 20 miles. Now is the time to treat your valued trees.  If the tree is thinning or you are seeing woodpecker activity, EAB will kill it in the next year of two. Proper treatment now can save it.

Sometimes trees may have a couple of upper branches that might not be salvageable.  If you decide to treat this tree, you will have the added cost of some of the upper branches removed.  You won’t have the high expense of removing the whole tree, and you still get to maintain your shade or curbside value.