Looks like Green Ash....you are definitely in the Emerald Ash Borer zone. I'd say the insect is killing and not last years' drought.

Fertilizer can help healthy trees correct nutrient deficiencies but will not help sick trees recover and will not protect against EAB. You needed a systemic pesticide 2-3 years ago to fight EAB....it would be too late now.

If it's an ash tree, look for D-shaped holes and areas of loose bark. They are tell-tale signs of emerald ash borer (in addition to the massive dieback). I'd say it is time to break out the chain saw and remove this tree.

Rodney

Too bad your local officials failed to educate residents about how to identify an ash. Here in Chicago I spent first six years of EAB event voluntarily surveying for private ash trees, then informing property owners about impending doom, well before their trees began declining from EAB. I was not someone telling everyone to treat their ash, only that there were more options than just loosing family tree.

I recall during our regions several year extended drought, how one clueless municipal arborist assumed that his communities whole collection of unprotected ash trees had suddenly began dying off from drought conditions in middle of August after loosing leaves. If only this poor sad sack misinforming public, would have traveled to Michigan to learn all about EAB on behalf of his residents. He would have known what he was experiencing was first of four year curve of death, when peak infestation of exponentially building borer populations had become large enough to mortally damage trees as early as August.

Or knowledgeable enough arborist to know that Ash had proven to be one of best extended drought tolerant species, surviving some four continuous years without rainfall, sustained from moisture produced by night time dew. Plus Ash literally being one of driest species, whose wood only contains some 12% moisture. Along with Ash only utilizing last three years of xylem for water uptake, and EAB primarily damaging phloem and cambium. Except for fourth instar stage of borers scoring limited sapwood before hunkering down for winter in bit of bored out xylem. Other Arborist were so lacking in basic knowledge during drought years, that they choose to wait before applying drench until drought broke. Afraid drenching tree during drought could be unhealthy.

What was unhealthy, was not protecting tree from EAB. And waiting until rainfall in June before finally drenching. Compared to Arborist who were also State certified pesticide applicators, knowing most primary requirement was applying drench product by April, drought be damned. As long as owners watered once before application, and then one or more times after drenching completed. Sure, drought could have very well played a role in a trees decline, along with EAB. But all we know now years after that drought, that not one tree drenched during that period had been adversely affected. While lesser species like Norway Maple and Linden severely hit by drought. Will never be the same again, and continue to partially or fully die off years later. Evidenced by branches who have been continually shortening their elongation rate since experiencing drought years. Plus roots from trees experiencing drought become mechanically damaged when pulling back in dried out soil.