Possible EAB infestation
I have 2 white ash trees in my yard in Crofton, MD. They both are showing dieback. One has loose bark and under that bark is signs of insect boring. I am a Certified Maryland Master Gardener and don't think this is an Emeral Ash Borer infestation, but would like to confirm it. Where do I go from here?
Look for the D-shaped exit holes of EAB. Read through the info on our webpage and study the photos: https://extension.umd.edu/hgic/invasives/emerald-ash-borer
You can also send us photos in a reply, and we'll look at them.. If you do, be sure to send both whole tree and close-ups of damage.
All ash in the U.S. will be attacked by this pest. So far, all untreated ones have died. EAB is in Baltimore County, so it is likely that you ash is attacked. You don't mention why you think it is not.