An ant infestation in a lawn is frustrating and ruins the appearance of the grass. Ants damage lawns in both small and large numbers, and simple tasks such as mowing become difficult as nesting mounds can sometimes damage metal mower blades.
Various species of ants cause lawn damage, including the western harvester ant, the carpenter ant, common black ants and the red fire ant. Use the mound sizes and any trail patterns to narrow down the species if the type of ant infesting the lawn is unclear. Some ants harvest and ruin the grass near nest sites while others protect aphids, small bugs that damage grass roots when feeding. Carpenter ants make unsightly trails over lawns to get from the main colony to smaller colonies around a site with wood, such as a house or garage.
Lawn damage caused by ants infestations depends on the ant type and level of infestation. Ant nests or underground tunnelling result in damage to the nest area and surrounding grass or plants, and anthills or mounds make the lawn uneven and mowing hard. Grass may "disappear" or thin out around the nesting sites or turn yellow or brown. Ants that make trails keep the pathways clear, killing any grass in the way. Some ants sting if the nest or colony is disturbed during landscaping, such as the red fire ant, and the insects may make their way from the lawn into a nearby structure.
Dry lawns are attractive to ants looking to nest, so keeping a lawn watered cuts down on the ant population. Ant bait traps, available at retail and gardening stores, attract the ants with a sweet substance and can be placed near nests or mounds to destroy the colony. Insecticides, such as liquid acephate or permethrin, are effective against lawn ants, but a large amount is needed for bigger colonies. Follow all directions on any insecticides to avoid harm or further lawn damage.
Ants do help control the population of other lawn nuisance insects, so consider the size of the ant problem before using removal methods. Chemical insecticides may damage the lawn as much as the ants, so spot applications should be used if possible.
Do not disturb mounds aggressively if the type of ant is unknown, as ant stings can be very painful.
- North Dakota State University Agriculture Extension; Lawn Pests in North Dakota; Phillip Glogoza; April 1997
- University of Minnesota Extension; What To Do About Household Ants; Jeffrey Hahn and Phillip Pellitteri; 1999
- Nutri-Lawn: Ants
- Insect Lore: Western Harvester Ant
- Washington State University Extension; Carpenter Ants: Their Biology and Control; Laurel D. Hansen, Ph.D. and Arthur L. Antonelli, Ph.D.; January 2005
- University of Nebraska-Lincoln Extension-Lancaster County; Ant Baits: A Least Toxic Control; Barb Ogg, Ph.D.; 2011