Some ants are too beneficial to control on fairways and roughs, yet too troublesome to ignore on greens and tees. As predators, ants can reduce populations of insects that damage rough and fairway turf. Greens can be protected from anthills with properly placed ant baits.

Baits target nuisance ants

Products from the structural pest-control industry can offer
spot treatments against golf course ants,
leaving helpful mounds untouched.

Daniel A. Potter, Ph.D., and Rolando López, Ph.D.

Ants can be a serious problem on golf courses when their nesting and mound building occur in high-profile areas. Superintendents often report problems eliminating these pests with conventional insecticides. Lately, we have been testing a new approach to managing nuisance ants on putting greens and tees, using delayed-action baits. The results have been promising and may be helpful to superintendents who need to spot-treat for mound-building ants in such areas. We are also studying the beneficial aspects of turf-infesting ants, especially their importance as predators on eggs and larvae of other turfgrass insect pests.

The ant Lasius neoniger can be a severe pest on
putting greens.

Surveys of nearly 5,000 ant mounds on putting greens of six Kentucky golf courses showed that virtually all of them were caused by one species, Lasius neoniger. This species also seems to be the main nuisance ant on golf courses throughout much of the United States (1,4). Problems arise when the worker ants excavate underground nest chambers, pushing up small mounds of soil that smother patches of turf, dull mower blades and disrupt the smoothness and uniformity of putting greens. Predatory birds may cause further damage by probing the nest openings. Lasius is also common in roughs, fairways, lawns and other sunny turf sites, although the mounds are less noticeable in such areas.

Habits of Lasius neoniger
Managing these ants requires that you understand their habits. Like all ants, Lasius neoniger is a social insect. It lives in colonies consisting of hundreds or thousands of sterile female workers, but only one reproductive queen. The nest consists of shallow, interconnected chambers, seldom more than 10-15 inches (25-38 cm) deep (3). Each passage to the surface is topped by a small mound. The number of mounds varies from just a few to 10 or more per nest and generally increases from early spring to late summer as the colony grows (2). The queen ant, with her eggs and larvae, remains underground and is fed and looked after by the workers.

Where do ant infestations on putting greens originate? As colonies build in late summer, new queens and males are produced. These winged reproductive ants swarm out of the nests for their nuptial flights in late summer or autumn (August-October). After mating, the young queens shed their wings and enter small ground cavities that they have constructed. The queens remain underground over the winter and normally don't lay eggs until the following spring. Successive broods are produced until at last the colony is large enough to produce males and winged females. Individual queens and colonies may persist for several years.

Lasius workers forage on the surface for protein foods, especially small insects and insect eggs (2). They also tend subterranean root aphids -- much as a dairy farmer tends cattle -- to obtain their sugary honeydew (a watery fecal product). Lasius neoniger is beneficial in most turf settings because it is a voracious predator of eggs and small larvae of cutworms, white grubs and other pests.

Several studies have shown how important this predation can be. For example, when 1,600 newly hatched cutworms were released, one by one, near Lasius nests on collars or putting greens, the ants immediately attacked and killed 62 percent of the larvae on their first encounter. In another test, turfgrass cores on which black cutworm moths had laid eggs were implanted into fairways or roughs of two golf courses, and the fate of the eggs was observed and videotaped over 24 hours. Lasius ants accounted for as much as 85 percent of the predation on eggs in untreated roughs in a single night. In treated fairways, where ants were less abundant, proportionately more cutworm eggs survived to hatch.

An active mound of Lasius neoniger on a creeping bentgrass tee can be flattened for good within three days after bait application.

Control methods
Regardless of their beneficial aspects, ants quickly become pests when they nest on putting greens. Controlling ants is difficult because fast-acting insecticides usually kill only a portion of the workers foraging on the surface, but fail to eliminate the queen. Pyrethroids such as bifenthrin (Talstar), cyfluthrin (Tempo), deltamethrin (DeltaGard) and lambda-cyhalothrin (Scimitar), and organophosphates such as chlorpyrifos (Dursban) often will suppress mound building for several weeks after treatment, but then the colony recovers, and new mounds appear.

Many pest-control operators who deal with ants around homes and other structures have found that commercial ant baits are an effective solution. These baits contain delayed-action insecticides formulated on granules with attractive food substances. The worker ants carry the bait back to the nest, where it is fed to the queen and her brood. Once the queen is eliminated, the colony dies out, and the mounds are not rebuilt. Last summer, we tested a range of these ant baits on golf courses. We started with small-scale "cafeteria" tests to learn which baits are most palatable to Lasius neoniger, and then evaluated spot-treatment of nests on putting greens and tees.

Once leveled by mowers, treated Lasius neoniger mounds were not rebuilt.

Conclusions
Our research showed that two commercial baits, Maxforce Granular Insect Bait (Clorox Co., Oakland, Calif.) and Advance Granular Carpenter Ant Bait (Whitmire Micro-Gen, St. Louis, Mo.) are highly effective against Lasius neoniger. Sprinkling a small amount of either bait around the mounds will eliminate a nest in about two days. A shaker can is useful for applying the bait. Once the mounds are raked or knocked down by mower blades, they will not be rebuilt. Minimum effective rates are still being tested, but about 1/8 teaspoon of bait per mound worked well in our trials. Withhold irrigation for at least eight hours to allow the ants to take the bait.

Both baits worked well in our tests, but Advance was more consistently effective and a bit more attractive to the ants. Maxforce, however, is less noticeable on putting greens because of its smaller granule size and dark brown color.

These baits are too expensive for broadcasting, but they are cost-effective for spot-treatment on putting greens. Golf course superintendents who have experimented with them also report excellent results. At present, neither bait is specifically marketed for use on putting greens. However, EPA registrations of both products list golf courses as an approved site. (Golf courses are on the label itself for Advance and are included under "non-crop areas" for Maxforce.) Neither registration specifies that the products cannot be used against Lasius ants on putting greens. Thus, their use is allowed under Section 2ee of the Federal Insecticide, Fungicide, and Rodenticide Act, as long as labeled rates are not exceeded. As with all pesticides, specific restrictions may apply in some states, particularly California.

Note that a similarly named product, Advance Granular Ant Bait, was not as effective in our tests.

Spot-treating with ant baits allows selective control, while preserving populations of beneficial ants in fairways and roughs. Regardless of whether one uses baits or conventional insecticides, ants usually are easiest to control in spring, soon after the mounds appear. At that time, the colonies founded by new queens are still small, and nests persisting from the previous year are weakened from overwintering. By controlling nests early, you can avoid the buildup of mounds on putting greens that occurs in late spring and summer.

Acknowledgment

The authors thank the staff of Champion Trace Golf Course, Nicholasville, Ky., for their cooperation.

References
1. Potter, D.A. 1998. Destructive turfgrass insects: Biology, diagnosis, and control. Ann Arbor Press, Chelsea, Mich.
2. Traniello, J.F.A., and S.C. Levings. 1986. Intra- and intercolony patterns of nest dispersion in the ant Lasius neoniger: Correlations with territoriality and foraging ecology. Oecologia 69:413-419.
3. Wang, D., K. McSweeney, B. Lowery and J.M. Norman. 1995. Nest structure of the ant Lasius neoniger Emery and its implications to soil modification. Geoderm 66:259-272.
4. Werle, S.F., and P.J. Vittum. 1999. The turfgrass ant: A necessary nuisance? Golf Course Management 67(2):49-52.

Daniel A. Potter, Ph.D., is a professor of turf and landscape entomology at the University of Kentucky in Lexington and author of "Destructive turfgrass insects: Biology, diagnosis, and control." Rolando Lopez, Ph.D., is a postdoctoral research specialist at the University of Kentucky in Lexington.