There are many different kinds of rose cankers. Some are slow to spread; others are fast .

When I have had a stem or cane go black, they have been the worst kind of canker and when I didn't react quickly, I lost the rose.

That said, in my opinion your rose is very sick.

If it were mine, I'd cut below the black half an inch and then I'd clean by cutting tools with bleach, leave the bleach for 30 seconds, dry the blade and then cut another half inch lower.

IMO you really want to get rid of what may be (something some of us here called) creeping black crud.

In your first photo, you have what appears to be a good healthy green cane maybe a half inch in diameter. BUT to the right there's a stem that is black. That black stem IMO has infected, and affected the cane below it that supports both stems. I think you need to lose that good looking cane because the support area is already dead on one side and will only get sicker. IMO you need to cut that support cane off until you get pith that is alive (Compare the colors as you cut down a stem- you will see a change.

This is one of those situations where you can learn a lot about how roses respond to problems and what you can do to try to direct their growth.

Thank you Ann for the detailed explanation!

I will chop off the infected support cane as you suggest. Does it matter that my area is expecting rain for the next 3-4 days? Do I have the luxury to wait until Tuesday? The forecast looks dry for a few days onwards then. I read that cold/wet weather exacerbates canker, I don't want the infection to spread and unwittingly help it along.

Thank you!

In my growing conditions, I wouldn't wait. On a smaller rose than yours, back when I was first encountering the creeping black crud, it took out small six inch canes in seven days in spring.

another thing to watch for. That big cane that I talked at length about: see the black part. Then look below it at a slightly less discolored halo, That halo is often a yucky magenta color that gets brighter as the season progresses. From what I've read in the plant pathology literature, that color is caused by the production of ethylene gas by fungi in the adjacent dead and dying cells.

Yours could be worse, but that discoloration has already started.

The sooner the sick canes are removed, the sooner the rose can 'know' that it's time to replace them.

Ann

Thank you Ann! I see the reddish halo under the blackened part, the smaller cane to the right isn't all black when you see it up close, there's a very prominent black line running through it. I will remove the cane and disinfect tomorrow morning. I will post pix so others can learn from this as well.

Yup, I agree with everything said here. It's heartbreaking to do at the time - but your rose should bounce back and be all the better for it.

Carol