knotweed is a serious problem. As the article says it can get thourhg concrete and all sorts so damages buildings. It's also very difficult and destritive to physically remove. Roots can go down many feet so the amount of soil to be dug out can be impractical.
Oddly the plant is I beleive female only in the UK. Not quite sure how it is able to spread based on that
It has no natural predator. Scientists are looking at the japanese bug the problem is if the bug itself has no predator, what keeps that in check? Could the bug evolve to eat other things if it runs out of knotweed, or do the two rely on each other?