I had the same problem. My cherry trees are (were?) Stella, Lapins, Minnie Royal and Royal Lee both on Mazzard root stock. Everything was planted this past spring so it was their first summer.
They had actually gotten lots of new leaves after we had that cool down just before it got really hot again. That second round of record breaking heat may have finished them off. The Minnie is definitely dead and the other three are kind of iffy. They have no leaves but are still pliable. Hopefully, I'll get some leaves sprouting out soon.
I watered them every 3 to 4 days for the "cooler" part of the summer and every two days during the hottest times.
I did have sun shade on the west side of all of the trees.

It was a unusually rough summer. I cant help but wonder if my Minnie may have pulled through if we have gotten our normal rains and cool down in August. Ugly ugly summer.

What im really hoping someone will jump up and say is that their cherries that they have had in the ground and this was their second summer did just fine. Crossing my fingers that this a case of a rough summer and not that they just cant make it here.

I lost four on Mazzard. I still have three on 3cr178 that are doing wonderfully. I had a 12 foot one that was severely wind damaged before the heat got to it. It had been in the ground for three years. It was as tall as my shed & was doing great before the wind blew about a third of it away. I planted the new rootstock this year and think it is definitely the best one for this area. One of them with west shade is still completely green. The other two are less shaded and have plenty of brown leaves, but also has alot of new growth. This is the fourth cherry rootstock I have tried & it is definitely the best one by far for me. It is also supposed to dwarf to 8-10'. Mine are already over 7' with 3' of growth the first year, so I'm not completely convinced on the eventual height. Hope that helps.

Desert Dawg that is exactly the information I was looking for! Thank you! It looks as if Mazzard just wont work out here, at least not on a crazy hot summer like we had. Colt seemed to squeek through. 3cr178 sound like best bet (but at a comprimise of having to have a small tree). Dave Wilson is also offering them now on GM61/1 rootstock and am very interested to see how it does here.

Come on bareroot season, im ready to try this again.

I've tried them on Mazzard, Z-Stem on Citation, Colt and 3CR178. I will replace the ones I lost with 3CR178. It is by far the best one for my soil. I live near the White Tanks/Verrado area. I think the trees will be plenty tall, you can only pick so high unless you are Andre the Giant......

Excellent information sir! Thank you! I will take your advice and go with 3CR178. I imagine our soil is close to yours, we are in the Laveen/South Mountain area on flood irrigation.

Seeing that we are both on the edge of town and get a little more chill hours I was wondering if youve ever tried Lapins or Stella cherries? Ive been considering giving them a go.

No, I've only tried the Royal pair. I think anything over 400 chill hours here is pushing it.

This may be the wrong place to post this question but...I have a couple of black cherries that seem to be dying on me. The first one started getting black tips on most of the leaves and then the leaves all started falling off. The part of the leaves that were not blackened were very green, shiny and healthy looking. We cut the tree back to about half it's height when a large part of a huge branch just fell off. It's sprouting like crazy from the cut branches. Now the tree next to it is starting to do the same thing. Any ideas? Does this sound like fungus? These trees are new to me as we inherited them with the house we recently bought.