Here's a link to the treatment I used to kill all the new yucca plant shoots at our property boundary that resulted from my neighbor trying to dig the plant up. It's been over a year now since the last treatment with no new shoots, so hopefully we got it. We had to re-treat new shoots once after the original treatment.
Turns out that digging them up is about the worst thing you can do - it expands the area of new growth to the boundary of the hole that was dug. I think that the active ingredient in Remedy is the same as in Turflon Ester, but Remedy is actually labelled for this use.