This is one of the leaf beetles in the family Chrysomelidae, that was introduced to NA perhaps a decade ago, to control purple loosestrife. They were only released after years of research and study both here and in their native range. They certainly can reduce purple loosestrife to a skeletonized plant, and some are saying that they appear to be having an impact on its growth, but there are still huge swathes of loosestrife all over. However, I do think that in some cases, the growth is less. I doubt they will ever eradicate purple loosestrife but if they can control it, that would be the best scenario.