Remove by hand [grin]. If it's in a place where you don't want anything to grow, you can use salt. We have a small space by the back door that we don't want anything growing in – just like to mulch it. So, we put down a bunch of salt and nothing grows there. Depending on how much you use … and how much things nearby tend to creep over … will determine how long that lasts. The area at the bottom of our driveway gets the grass from the easement edging into it, so we have to salt that every year. But the back door area lasted 2-1/2 yrs from the 1st application. We get 25 lb. bags of salt to make it a really cheap solution.
Here's a link with lots of info on it: