What weed is this an how to treat?
This looks like henbit, which is a common winter annual. It germinates from seeds in the late fall. If you leave it alone it will grow rapidly in the early spring and produce purple flowers before dying in the warm weather. You can treat it now with a broad-leaf herbicide that contains (2-4-D, MCPP and dicamba). Choose a day to spray when temperatures will at least be in the 50's for the next couple days.
If you don't want to spray, mowing weekly throughout the winter can provide some control. It won't kill the henbit, but you can prevent it from flowering and going to seed which will reduce your problem next year. This Clemson publication provides more in-depth information.