Ants don't cause major damage to lawns, according to entomologists with Penn State University. These little creatures can actually be beneficial to the home landscape because they aerate the soil and some types feed on other, more harmful pests. Ant hills can become an annoyance, though, when they proliferate and cause the soil under the turf to loosen. If they get large enough, ant hills can smother and kill the grass beneath them. Frequent spot treating is the best course of action.
Rake any ant hills on the surface of the grass. Completely flatten them.
Pour insecticide, at the rate suggested on the package, over the mound area.
Water the entire lawn to allow the insecticide to sink into the soil.