Damage
Distant: Ant mounds are only a problem on golf course tees, greens and fairways, or where turfgrass is mowed very short (< 1.0 inches). Ant mounds are undesirable on tees and greens because they interfere with putting and may be unsightly. In addition, stepping on ant mounds, or running over them with mower wheels may result in 0.5 to 1.0 inch diameter round patches where the turf is covered by soil (Images D, E, and F).
Up close: Round-based conical mounds about 1-2 inches in diameter with a hole in the middle. They consist of finely ground soil or sand (Image G). Ants can be observed coming and going when the temperature is 60 F or warmer. The mounds are most obvious if the area has not been disturbed by mowing or irrigating for several hours.
When damage would be found: Late May to early September with peak activity in June.
Host: Although ants can be found in all types of grass, they are only a problem on tees, greens and fairways of golf courses.
Site: Ants are found in any type of turfgrass, but are only a problem on tees, fairways and greens of golf courses. Ants may be more abundant at sites with sandy soil.
Description of damaging stage: The adult workers make the mounds. They are about to 1/8 inch in length.
Management
Sampling: Look for mounds starting in May. On golf courses, the mounding peaks in June and slowly declines from July through September.
Preventing Pest Injury to Turfgrass: Home lawns, recreational turf and golf course roughs can be managed to avoid insect injury without insecticides by using proper fertility, mowing at a height of 3.0 to 4.0 inches, and watering during dry periods. This will build a dense stand of turf and a diverse community of insects that will keep turf pests under control. All lawns in Michigan will typically start off lush and green in the spring and will go dormant and turn brown during periods of little rain. Information on the use of insecticides to treat turf pest problems is only meant to be used for the unusual cases where turf damage from pests becomes unacceptable. Even then, insecticides should only be used in areas of a lawn with severe turf damage, and only until a dense turf is re-established.
Using insecticides: Use insecticides judiciously, temporarily, and only in response to unacceptable turf injury. Mow lawns before spraying or spreading an insecticide to avoid leaving a pesticide residue on flowering weeds, which may be harmful to pollinators. Many insecticides are poisonous if ingested, and therefore must be stored in places where they cannot be found by children. Use the rate recommended on the label for the pest you are attempting to control. Wear rubber gloves, safety glasses (or goggles), rubber boots, long pants and long sleeved shirts when mixing and applying insecticides. The most caution is needed when mixing a concentrated insecticide in water, because skin contact with the concentrated insecticide in the original container is more dangerous than contact with the diluted insecticide after mixing. Water the turf immediately after applying the insecticide to wash it to the base of the plants or into the soil and allow the turf to dry before allowing access by people and pets.
Control of Ants on Golf Course Tees, Greens and Fairways: There is no need to control ants in lawns. They do not cause turf injury and they help suppress turf pests by foraging on insect eggs and small larvae. Simply raising the mowing height to 3 inches or higher will avoid any visual detection of ant mounds. For golf course tees, greens and fairways, the neonicotinoid insecticides clothianidin and thiamethoxam, are highly effective for long-term suppression of ants. If there is a tournament coming up, a spray of a synthetic pyrethroid such as deltamethrin, permethrin, cyfluthrin, bifenthrin and lambda-cyhalothrin will give a quick and sharp reduction of ant mounding, but they will rapidly recolonize because the insecticide residue on turf blades is removed by mowing and breaks down in sunlight.
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