As
@Lucy68 and
@crawgarden said, you will have to use a brush killer. If this is a part of the yard you don't care about you can spray the entire area. I once had a similar situation but didn't want to kill a lot of the yard so I walked the area and sprayed the weeds individually. Wait a week then walk through and spray what you see. The population should decline after several weeks. Every Saturday grab your spray bottle and get those guys.
