They are kinda pretty. Why Should they be eradicated?
I assumem they are like the elm-beetles that are currently killing off all our Elm threes. They are slowly moving upwards from the German border and will reach the northern tip of Denmark in a couple of years. Meanwhile new elm trees are growing happily on the German border and a bit north of it. It is not the end of the world. Just save some seeds for when they have passed on.
Sure. All you have to do is dig up all the emerald ash trees and ship them to China and let them figure out what to do. China would probably develop a green glass tree and the borers would starve to death.