The problem may not be where the dieback is. The problem could be that something has been attacking the root system, and the plant is "self-pruning" to make itself the right size for its challenged root system. It could be something fungal, but the first thing you might do is hunt around for suspicious holes--as in gopher holes. If a critter is eating the roots, that could explain a lot.

Kay

I've had some of the foliage issues on one particular rose and after the first flush of bloom, if the foliage is getting ugly, I have cut the whole rose back to about 6 inches off the ground. I am not an expert rose grower by any means, it's just the easiest way for me to live with roses, without using any sprays. The rose has always come back for me and sometimes I get another flush of bloom later in the season. And they are growing in a perennial bed so by the time I'm ready to be done with the foliage, there are other plants around them getting large enough to hide the missing rose.

Something bad is happening, because I noticed yesterday that some myrtle growing along the retaining wall in front of the rose has turned brown and died. Not all of the myrtle, just near the rose; so you could be right Kay. I think I'll give it(rose) another couple of weeks to begin some recovery, if it still looks stressed I'll prune it back as prairie suggests.

One good thing came of this. Just awhile ago I was pulling away the dead myrtle and found the rose's metal name tag still attached to the very bottom of it. All these years I couldn't remember what it was called. Zephirine Drouhn

Here is a link that might be useful: Zephirine Drouhn

hope it recovers. That's a lovely rose.

Another possibility might be soil trouble--manmade soil trouble. After we had some work done on our house last year, I was in the nick of time stopping one of the workers from emptying a really nasty bucket of whatever it was they'd been using in a far corner of the yard, where it surely would have affected my camellias and Japanese maples. Disaster was averted, but if they'd been damaged I would have been scratching my head about what happened.

Kay