While ants in the lawn may appear to be pests, recent research indicates that they actually play an important, beneficial role in grass. For example, ant populations control many insect pests such as cutworms and grubs. Their digging also serves to aerate soil. They hunt for eggs of pest insects, remains of small animals, and other debris that is rotting both within and on soil. Most often they are scarcely noticed by homeowners. Ants look for food over a vast amount of space—feeding on vegetables, seeds, bugs, and flowers. Because of the help that they provide in controlling pest insects, it is rarely a good idea to manage ants in lawns. Thankfully, this is one less thing to worry about. Leaving ants in lawn alone is actually a good thing.
Ant mounds, however, may be unattractive and get in the way of mowing. Ants that build mounds may be destroyed by lightly soaking the mounds with a labeled liquid insecticide. Emulsifiable concentrates, powders that spray, and granules are good ones to try. Only products specifically for ant control in lawns should be used and, as always, instructions should be followed carefully. If using a sprayer with a hose attached, agitation should be consistently employed during spraying. After the mound is treated, you can water and roll or rake the mound so it is level with the ground.