This is the first I've heard of it.

I haven't seen that on any canes I've cut and I've cut a lot with symptoms.

I wonder if that coloration is because of less than pristine secateurs (on a single blade) because of the pattern it exhibits.

Back when Epstein and Hill wrote the Etiology of RRD paper, they mentioned staining of canes of affected roses. But they were talking about after cutting the cane and applying stain to that surface. rose canes stain with iodine to show the presence of starches - which meant that there was a difference between those rose canes and totally infected ones where there was no starch-sugar conversion of (and related poor winter survival). (See the test for starch of a match stick and medical grade iodine.)

At Jim Amrine's lab, he had some iodine and I put in on a stem that had 1) mites and 2) RRD symptoms and the iodine stain didn't work the way it was supposed to.

Thanks, Ann. I also had wondered if it might be pruner gunk. Sounds like the writer may have been confused, but I guess we don't know for sure yet.

I am in process of trying to kill a huge rose that is practically undiggable (Mme. Plantier that had spread 20' wide on a steep bank). In a second round of cutting back and painting Roundup, I looked for stained phloem and didn't see any. But I didn't cut all 30 stumps this time (skipped the dead ones) and am not sure I did the RRD ones.

Thanks Henry for noticing that this question needed to be raised. It would be handy if staining did turn out to be a symptom.

Heartbreaking to lose an old big wonderful rose, Michaelg.

I was fonder of Mme P than any rose in the garden. Totally carefree and so lovely in bloom. I planted her as a band around 1985.