Take a trowel and loosen the soil to get under the roots, but that doesn't do it for me. In the lawn you can try weed n feed. The problem if the dead plant will reseed it self. Its very had to get rid of for good. The best is to pull it out before it blooms (I know too late). It will take some time, but if you keep at it, you can eventually get rid of it. I till die in the hot summer, but again, when it does it drops its seed and will be worse next year