The presence of ant mounds on the golf course can be disruptive to playability, especially in closely mown areas like tees, fairways or putting greens. The mounds can disrupt ball roll, and the soil brought to the surface can bury turf and be detrimental to mowing quality. As I travel the Midwest on USGA Course Consulting Service visits this summer, mounds caused by turfgrass ants (Lasius neoniger) will become a more prevalent topic as colonies grow and activity increases. However, the optimal time to control ant populations in many areas of the Midwest is right about now.
Ants are social insects; they assemble themselves in colonies that have a single, egg-laying queen. If you can control the queen, you can control the colony. When temperatures in the spring increase, ant activity and the number of mounds also increases. Once you see mounds begin to appear in the spring, it is recommended to apply an insecticide to control ants while they are weak from overwintering. A properly-timed insecticide application may stress the colony enough to cause it to collapse.
Conventionally, contact insecticides like lambda-cyhalothrin or bifenthrin are used to provide control of worker ants at the surface for a few weeks. Applying longer-residual insecticides like clothianidin or thiamethoxam once ant mounds are first seen in the spring can provide several weeks of control. A combination product like Acelepryn Xtra, which pairs the commonly used chlorantraniliprole with thiamethoxam, is often applied in the spring for season-long grub control, but the addition of thiamethoxam brings the benefit of enhanced ant control.
When treating ant mounds, it is recommended to spray the affected areas and to broadcast apply the insecticide in the rough adjacent to the closely mown surfaces. The label of the insecticide Meridian (thiamethoxam) recommends treating the affected area plus a surrounding buffer of 30 feet. Oftentimes, ants have more populous and prolific nests in the rough, so applying insecticide to the rough closest to affected areas of closely mown turf can help eliminate future migration.
Ant baits can also be used to control ant populations. Baits are most effective when applied on dry turf when there isn’t going to be any rainfall or planned irrigation for a couple of days following the application.
When considering how to best control turfgrass ants at your facility, remember that you have many options for control, but the timing of control should also be considered to achieve the most-effective, longest-lasting results. If you have any questions about ant control at your course, please reach out to your local USGA agronomist.
Central Region Agronomists:
Zach Nicoludis, regional director, Central Region – znicoludis@usga.org
Tom Gould, agronomist – tgould@usga.org