It looks like you have a case of stem rot, most likely caused by a Fusarium type fungus. Because it is on a common brug, I would toss the plant and sterilize any cutters that may come in contact with it.
Here's an article written by Delisa Harvey on stem rot that you may find helpful.
Thank you Fred I will pull it up.. bag it and toss in the trash.
Always wanted to see CG in full flush :} I just popped the limb off to take pics so the tools are safe!.I checked the others in the garden and they look fine.
here it is in the yard..