Canker on rootstock (plum greengage)

I am a first-time grower of plums and hazelnuts (so far), and grateful to find this community!

I have been trying to diagnose a problem on the rootstock of a European greengage plum, and think it is likely bacterial canker (photo included).

From reading the threads here, it looks like my only bet is some surgery to remove diseased wood. Am I correct in my diagnosis, and are there any special considerations for cutting out canker on the rootstock as opposed to the scion?