Yep.For the nth time Ammonium Sulphamate. It kills the root.
Buy a few kilogram, dilute to taste (or maybe not!)
I tend to use a plastic syringe to apply to specific plants - wearing gloves, crush the leaves and stems, and apply. With mares tail/ horsetail, I snap the stem and shove it down the stem. Garden has gone from being over-run a few years ago to only finding two new shoots this year. Not one of the neighbours ever commented on me crawling around the garden, under bushes, under the hedge, safety classes and gloves, syringe in hand . . .