I am now controlling by cutting out and then blowtorching. I have tried each of these separately and they work pretty well separately, but together they nail it. You need to cut until the deeper-green colored wood is all gone, only lighter green or ivory wood should be showing. Then blowtorch for maybe 30 seconds, get some smoke going. If it is girdling the whole limb this method won’t work, but for me only smaller limbs get girdled and those I completely remove.
In 22 years only one tree needed removal, it got completely covered in knots. I could have pruned it back but concluded the variety was too susceptible to keep around. Rosy Gage was the variety. For most of these years I controlled by either just cutting or just blowtorching. That kept me in plums but I had too many return infections (maybe 10-20% would come back) so I am now doing both.