Ants in Lawns

There are many species of ants which occur in lawns and other turfgrass areas. Most ants do not require controls and are considered beneficial. Ants move approximately the same amount of soil as earthworms, loosening the soil in the process and increasing air and water movement into the ground. They keep the ecosystem clean of dead insect carcasses and aid in the destruction and decomposition of plant and animal matter. By carrying bits of plants and animal remains into their nests, the soil is fertilized and nutrients recycled through the ecosystem. And finally, ants are among the leading predators of other insects, helping to keep pest populations low.

However, ants may become a nuisance by constructing mounds or small hills in the lawn or by invading the home in search of food. The ants found in Iowa lawns are not biting or stinging pests. The fire ants of the southern U.S., well known for their aggressive behavior and painful stings, are not present in Iowa.

Ants are social insects that live in well-organized colonies. Nearly all of the ants in a colony are the wingless sterile females, called workers, typically seen on or around an ant hill. They do the work of the colony which includes enlarging and maintaining the nest, caring for the queen's offspring (larvae that reside within the nest), and searching for food to bring back to the nest. In the spring or fall ant colonies may produce winged males and females called swarmers. These harmless reproductives disperse from a well-established nest to begin new colonies.

Ant Mounds. Soil nesting ants construct mounds or small hills by bringing granulated soil to the surface from the nest below. These mounds may be unsightly, may cause lawn unevenness, and if large, may smoother out the surrounding grass.

To avoid some of the worst ant hill activity rake or "wash" (with a water stream from the garden hose) on a regular and frequent basis ant hills that appear above the grass tops. The need for such maintenance will be greatest during periods of prolific ant nesting activity (such as during periods of wet spring weather). If necessary, you can spot treat ant hills with an insecticide such as diazinon or Dursban. Rake the ant hill flat and sprinkle granules onto the soil surface or drench the mound area with diluted solution. Read and carefully follow instructions on the insecticide label. If granules were used, rake the area lightly after application. Irrigate the mound area to move the insecticide ingredient into the soil and away from the surface where it may be exposed to people, pets or wildlife. Keep children and pets away from the treated area until the grass has dried. Ant mounds can also be treated by pest control operators or lawn care professionals. Overall lawn treatments specifically for ant colonies are seldom necessary.

This article originally appeared in the June 19, 1998 issue, p. 82.


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