Chamberbitter. I hate that stuff. Good luck getting rid of it. Goes from sprout to being able to spread seeds in about a week. Preemergents may work to prevent spreading, but nothing I've tried has killed the stuff without taking out everything else around it. That stuff's all over my yard. I think Roundup works, but I'm not really interested in resodding my entire 3/4 acre yard. If you pull them, be sure to get the roots and don't bother to shake the dirt off. You're just spreading (more) seeds if you do.