Thank you, Mike and Christopher.
Yes, all canes ended in the dreaded telltale thorny red growth.
As soon as those two buds have finished blooming, I will dig up and discard the plant as aseptically as possible. By the way, a second plant of the same cultivar had the same telltale growth and is now dead, ostensibly from winter damage (alternating growth spurts and dieback with the crazy false starts of early spring). I still need to dig up its root.
Thank you so much for confirming the diagnosis. That will help to motivate me to get rid if these plants.
Carol
