Hi there I have a huge white ash tree that I was tending to, fighting off the emerald borers and who knows what else. let me just share my experience, my tree is still going strong, especially after I painted the trunk with thinned flat wall paint to protect the bark from scalding heat. Emerald ash borer beetle is rampant this year and it already killed several trees on the block. I didn't dare to use stronger insecticides on a weakened tree so I used one of those Bayer Rose Ortho granules that feed the plant but also permeate it with insecticide. I found lots of holes on the trunk after a week and lots of dead beetles around. I plugged the holes with caulk, can use play-doh too :), watered and pruned dead branches or ones that showed distress, sealed the cuts off with paint. Now my neighbors are doing the same seeing how my tree recovered. The two ash trees on both sides of mine (at my neighbors) are dead but mine is surviving, for good I hope.
It would help if you posted a pic of your tree? Thanks :)

You should hire an arborist to examine your tree to assess the extent of the damage. If the tree is close enough to buildings, parking areas or places where someone could be injured if it fell you should do so immediately. I had a large ash in my front yard just about 50 feet from my house that appeared to be dying. The arborist tested it and found that the entire center of the tree was decaying and urged us to have it removed. When we did we found that although a few of the branches were still leafy, most of the trunk was hollow and rotted. Much of it crumbled as it was being cut down. If it had fallen on the house it could have demolished about 2/3 of the building, the bedroom and living areas.