Several species of ants are common landscape residents. They nest in places that meet their needs: suitable soil type and drainage, convenient food sources, and in some cases, sheltering rocks or logs. We most commonly share greenspace with field ants, pavement ants, and larger yellow ants. Mounds of soil excavated by ants make turf bumpy and smother grass around the openings (Figure 1).
Repeated strikes of tall mounds can dull mower blades. On the plus side, lawn ants rarely are household invaders. Their diets typically include live or dead insects and sweet substances, often honeydew collected from aphids and scale insects. Field ants and larger yellow ants are common species.
Types of Lawn Ants
Field ants resemble carpenter ants but nest in the soil rather than moist wood. The workers vary in color from black to red and shades in between. They forage widely for food so individuals can be seen on sidewalks, decks, and patios, but they only occasionally wander indoors. Their low profile mounds may be 8” to 10” in diameter and can be next to walks or landscape timbers.
Larger yellow ants, also called foundation ants, go about their daily routine largely unnoticed. However, this changes when winged males and female reproductives swarm. Mating flights appear suddenly, often after a rain, and usually during late summer afternoons. Flying ants can be alarming, but this species does not nest in structures and is not interested in stored foods.
Yellow ants nest in soil, usually under rocks, around or along foundations, or in open areas in yards. They bring up large amounts of soil as they excavate their below-ground galleries. The ¼-inch long wingless workers collect the sweet liquid waste (“honeydew”) produced by aphids and other sap-feeding insects that feed on plant roots.
Pavement ants are small, dark ants that prefer to nest under large rocks, sidewalks, and building slabs. Piles of fine soil particles near sidewalk cracks are their signature. These ants will carry almost any available food item back to their nest. This species will enter structures through cracks and crevices in search of food.
Managing Lawn Ants
Control of lawn ants is generally unnecessary unless they are entering the home or causing significant disruption in the landscape.
A colony often can be eliminated by spraying or drenching the nest location with a liquid insecticide such as Ortho Bug B Gon Insect Killer for Lawns (bifenthrin + z-cypermethrin),
Spectracide Triazicide Lawn Insect Killer (g-cyhalothrin), and Bayer 24 Hour Grub Killer Plus (trichlorfon).
Large colonies will require greater amounts of liquid to move the insecticide throughout the network of underground galleries within the nest (using a bucket to apply the diluted insecticide concentrate is an effective method). Follow label directions for treating ant mounds, paying attention to precautions for mixing and application.
Another effective and convenient way to control some species of outdoor and indoor-nesting ants is with a granular bait product, such as Combat® Ant Killing Granules. Sprinkle the bait in small amounts beside outdoor ant mounds, along pavement cracks, and other areas where ants are nesting or trailing.
Reducing Entry into Residences
Ant entry into homes can be reduced by caulking around door thresholds, windows, and openings where utility pipes and wires enter buildings.
Ant entry can further be reduced by spraying one of the above-mentioned liquid insecticides around the outside perimeter of the building. Consider applying a 2- to 6-foot swath along the ground adjacent to the foundation, and a 2-to 3-foot band up the foundation wall. Also treat ant trails and points of entry into the home, such as around doors and where utility pipes and wires enter from outside.
Spraying Whole Lawn NOT Recommended
In Kentucky, spraying or applying granular insecticides to the entire yard is not recommended, and will seldom, if ever, solve an ant infestation indoors. Whole-yard treatments also eliminate beneficial ants, which help to keep other damaging pests of lawns and gardens in check.
By Lee Townsend and Mike Potter, Extension Entomologists