It would be a need for more water inside the plant. Maybe you will have to rig up some shade for awhile, to help get them through the early stages, the shade reducing the dehydrating effects of hot sun.

If they were in claylike soil balls which were on the dry side when purchased, left intact they may actually be shedding water off the outside of the ball instead of soaking it up. I see many field-grown trees here delivered to new developments, left sitting around on the ground apparently unwatered for awhile, and then being installed in a droopy or even wilted condition that may persist afterward for quite a long time.

Thanks for your input, I really appreciate it. I checked before purchasing my trees, and their root balls were moist, and I have tried to not let them dry out since planting. Okay, so then my answer would be more frequent deep watering, correct? Any other suggestions to stop the wilting?

You asked:
"so then my answer would be more frequent deep watering, correct?"

No, because the roots aren't yet deep. Instead, the roots are currently confined to the rootball that you set into the ground.

So, the water needs to be applied directly to the original rootball.

Did you perhaps bring these trees home in the back of a pickup going 70mph down the freeway? Sounds very much like wind burn. Best you can do is to keep the trees watered until they establish. They might loose their leaves but will probably grow new ones this year.

As well, if you can rig some sort of temporary shade, it might help. If they were grown or were stocked in a shade area in the nursery, the all-day sun may be a bit too much. Shade during the heat of the day, and then gradually decreasing it, might help. It CAN adjust, but if it has to all at once, it might be a bit too much.

I've not had much to do with ash tres, but in some trees, wilting is a protective mechanism - it limits trasnspiration - the loss of water through the leaves. Do the leaves perk up early in the morning?

Even if the leaves all fall off, eventually, if the roots are healthy, the tree should grow new leaves. I would water the root ball (not TOO often, or it will rot), shade it - maybe mist it in the heat of the day - and mulch well around it, if you haven't - as wide as possible, no deeper than 4", and no mulch in the 2-4" next to the trunk.

LOL....texasredhead, sounds like you speak from experience