Bacterial Canker?

Another reason why I'm feeling cavalier about my plum tree. For a number of year it has been oozing gum from a number of lesions, including quite a sizeable area low on the main trunk.

The oozing and dieback of smaller branches do suggest bacterial canker, but I'm not absolutely convinced. I've never had any young growth die back or every seen any spotting on the leaves. Also, the damage first appeared after a particularly cold spring with severe frosts, and new lesions this year also correspond with possible damage from severe frosts.

I can remove small branches, but not the bigger area on the main trunk, so we just have to hope the  tree can live with the problem, as so far it has done. Branches affected are more likely to produce blossom, not something this tree is naturally adept at!