Question: What is the wiry little weed with small purplish-white flowers? It is all over my yard every fall.

Answer: That's roadside aster. It is a weed of neglect, showing up primarily in dry, under-maintained parts of lawns, especially near curbs, walks and drives. While you could apply a pre-emergent in the spring or a post-emergent herbicide during the summer, roadside aster will quickly die away as you take good care of your turf.