We have an abundance of purple queen and have been digging out roots and know this kills, but it's time consuming. Is there any spray or such to kill these wonderful but very hardy plants?
How to Kill Purple Queen
Certified GKH Gardening Expert
You could spray them with glyphosate (Round-up), but apply with care; as they can kill other plants besides purple queen. The article below will tell you how to apply Round-up without causing harm to other plants nearby.
However, I would recommend having other people do the work for you: I do know that many people would love to have purple queen so perhaps you could enlist interested family, friends, co-workers, neighbors to come over and dig up a plant for themselves.