lJSCiA.~ "M' USGA provided partial funding for this research.

Turfgrass ants: Biology dictatesstrategies for controlUnderstanding ant biology can help superintendents manage these nuisance pests.

Daniel A. Potter, Ph.D., and Reid M. Maier

RESEARCH

Mound-building nuisance ants can be oneof the most troublesome pests in golf coursemaintenance (Figure 1). Ant mounds can bevery abundant in greens and tees with high-sand root zones. Besides being unsightly, antmounds dull mower blades, clog machineryand smother closely mowed grass. On greens,ant mounds disrupt smoothness and unifor-mity and can negatively affect the game.

Superintendents often report difficulty ineliminating ants with insecticides, and antproblems seem to be on the rise. Possible rea-sons for these trends include the decline ofresidues of chlordane and other persistent soilinsecticides used in the past and the replace-ment of broad-spectrum insecticides (forexample, diazinon) with more-selective soilinsecticides, which has allowed ant popula-tions to resurge,

Habits of the turfgrass antNearly all nuisance ant problems on golf

courses in the cool-season and transitionalzones are caused by Lasius neoniger, the so-called turf grass ant. This cosmopolitan spe-cies typically nests in open, sunny areas.It is not the same as the red imported fireant, Solenopsis invicta, a pest in the south-ern United States that inflicts painful stingswhen its mounds are disturbed. Turfgrassants do not bite or sting humans.

Like all ants, 1. neoniger is a social insect.Workers, the form seen at nest entrances,are light to medium brown and about 0.10inch (2-2.5 millimeters) long (Figure 2). Thesubterranean nest consists of interconnectedburrows and chambers and is seldom morethan 10-15 inches (25-38 centimeters) deep.Mounds are formed from particles that theworker ants bring to the surface while exca-vating and enlarging the nest. Each moundmarks a different nest entrance. The num-

ber of mounds varies from a few to dozensper nest and increases from early spring tomidsummer as the colony grows. Besidesworkers, the nest contains a single reproduc-tive queen as well as immature stages (eggs,larvae and pupae) that are collectively calledthe brood.

In general, ants are beneficial to turf-grass. They are the main predators on eggsand small larvae of grubs, cutworms andsod webworms, helping to keep those pestsunder control (1), The burrowing and nest-ing activities of ants promote air and waterinfiltration and help to incorporate organicmatter into the soil where the nutrients areavailable to the grass roots.

The ant life cycleFor most of the growing season, the queen

lays eggs that develop into infertile femaleworkers that cooperate in cleaning and enlarg-ing the nest, gathering food, defending thenest and tending to the queen and her brood.In early summer, she begins laying eggs thatdevelop into winged reproductive forms.These males and young queens emerge in latesummer. After mating, the males die, and thenewly fertilized queens fly or crawl to new siteswhere they will start new colonies.

We monitored queen emergence by plac-ing pitfall traps around putting greens in2003 and 2004. In both years, there wereseveral pulses of emergence from mid-Augustto mid-September, usually following periodsof rain (4). The queen has a fatter abdomen,is much larger than the workers and may beseen crawling on greens and other closelymowed grass (Figure 3). Young queens chew

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in late summer completes the cycle. Once anest has been established, the resident queenmay survive and lay eggs for several years.

Recommendations for controlling turf-grass ants usually emphasize early treat-ment, soon after the mounds appear. Wedetermined the seasonal pattern of mound-building by counting active mounds on 10sand-based bentgrass tees monthly on eachof two Kentucky golf courses (4). Moundsfirst appeared in February or March, peakedin May and June and declined by late sum-mer (Figure 4).

Feeding habitsWorkers of Lasius neoniger forage for

insect eggs, small insects, insect fragmentsor seeds. Once food is found, the workerdeposits a pheromone trail as it returns to thenest. Other workers follow this trail - andreinforce it - to find the resource discoveredby the scout. Workers also obtain carbohy-drates (sugars) by feeding on nectar fromnearby plants.

Many ants also obtain carbohydrates byfeeding on honeydew from aphids or othersap-feeding insects. The honeydew, essen-tially aphid diarrhea, contains sugars, aminoacids, minerals, vitamins and other nutrients.Often the ants tend the aphids like dairy cat-tle, defending them from predators. Whenan ant strokes an aphid with its antennae,the aphid relinquishes a sugary droplet fromits anus. The ant swallows the droplet andcarries it back to the nest, where it is sharedwithin the colony.

Lasius neoniger has a special relation-ship with root-feeding aphids (Geoica spe-cies), which the ants maintain in or neartheir nests, even in winter (Figure 5). As theaphids multiply, the ants care for and protectthem. Turfgrass that receives supplementalnitrogen and other nutrients often supportslarge numbers of root aphids that provideample honeydew for ants. The ants also mayeat some aphids to supplement their diet.The aphids themselves do not seem to harmthe grass.

feeding on honeydew of root aphids (shown here) andother tiny insects that suck plant sap.

have enough nutrients to lay additional eggs.The queen stays in the nest and lays moreeggs that develop into normal workers. Thecolony grows rapidly in late spring and earlysummer as the ants enlarge their nest and for-aging area and increasingly more workers arereared. Production of males and new queens

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off their wings before burrowing into the soilto overwinter.

Egg-laying begins in late winter. Queensinitiating a new nest first lay a batch of 10-20eggs. This first brood will develop into tinyworkers called nanitics, which begin forag-ing for food for the queen, ensuring she will

RESEARCH

Feb Mar Apr May Jun Jul Aug Sep Oct Nov

Figure 4. Seasonal abundance of ant mounds on 10 tees on each of two central Kentucky golf courses.

Ant mound locationWe have observed - as have superinten-

dents - that ant mounds tend to be con-centrated around the edges of sand-basedputting greens. Why? We suspected thatthe structure, depth and abrasiveness of thehigh-sand root-zone mix are unsuitable for

88 GCM November 2006

Figure 6. Several factors contribute to the concentration of ant mounds around the perimeter of sand-basedgreens. Main nests are outside the collar in natural soil; subnests, representing garrisons of food-gatheringworker ants, encroach inward as colonies expand their foraging territories. Root aphids, a source of carbohy-drates, are abundant in natural soil associated with main nests, but are largely absent from greens. Abundantprotein food (dead and living insects), closely mowed grass and sandy soil all promote incursion into greens,with excavation of subnest chambers and mounding. Dashed lines show the zone where superintendents shouldfocus their control efforts.

permanent ant nests and the soft-bodied rootaphids from which the ants get a portion oftheir food. If so, mounds encroaching ontogreens might represent secondary nest cham-bers connected to main nests (with queenand brood) located outside the collar in nat-ural soil. If the main nests are just outsidethe green, control efforts should focus there,rather than on the entire putting surface.

Testing the hypothesisWe tested our hypothesis by mapping

several hundred mounds on 10 sand-basedgreens on each of three golf courses (3). Rootaphids were sampled by pulling soil coresalong transects centered on the collar andextending into the green or rough. More than90% of the ant mounds were located within6.5 feet (2 meters) of the perimeter, and only3% were more than 10 feet (3 meters) intothe green. Root aphids were associated withant nests in natural soil, but nearly absentfrom the high-sand root-zone mix of greens.Obviously we could not dig up greens atour cooperating golf courses to excavate antnests, but our sampling ofUSGA sand-basedgreens at the University of Kentucky TurfResearch facility confirmed that the mainnests, with queen and brood, were located innatural soil outside the collar. Nearly all ofthe nest chambers in the greens themselvescontained only worker ants (3).

We cannot say for certain why the mainant nests are largely absent from sand-basedgreens. Perhaps the high moisture levels arenot conducive to brood rearing, or the absenceof root aphids plays a role. Alternatively, thehigh-sand root-zone mix may be structurallyunsuitable for permanent nests.

Attracted to greensWhy does L. neoniger expand its second-

ary nest chambers and mounds into greens?As a result of mowing, the edges of greenshave abundant dead insects, eggs or insectfragments that are scavenged by worker ants .Indeed, when we placed diced black cutwormsaround the edge of a sand-based green, work-ers quickly congregated on the food items,in some cases excavating nest entrances withmounds where none were present before.Opening new nest entrances allows workers totake food items underground quickly, alleviat-ing losses to competitors. The high-sand root-zone mix seems suited to tunneling, if not forpermanent nests. Indeed, in other experiments,

we showed that the ants respond to both low-cut turf and sandy soil by increased mound-building. Short-cut grass may also favor moreefficient foraging from the standpoint of trailpheromones. Although ant nests are abundantin roughs, lawns and other high-mowed turf,we tend to see few volcano-shaped mounds insuch areas. In high grass, it may be easier forthe ants to strew excavated soil than to pile itaround nest entrances.

To summarize, our work indicates thatmost ant mounds on sand-based greens areassociated with subnests constructed by work-ers to expand the area over which the colonycollects food resources (3). Such subnests areconnected via underground runnels to mainnests located just outside the collar in natu-ral soil. Encroachment of mounds into greensoccurs as colonies grow seasonally and expandtheir foraging territories, which accounts forthe concentration of mounds being aroundthe perimeter (Figure 6). Lasius neoniger huntsand forages on sand-based greens but does notpermanently nest there. Clusters of moundson such greens represent garrisons of workerants on hunting forays.

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RESEARCHImplications for managing ants

Superintendents often find that spray-ing greens only temporarily suppressesant mounding. Fast-acting insecticideskill workers foraging on the turf surface,but usually fail to eliminate the queen in herunderground nest chamber. Several pyre-throids, including TalstarOne (bifenthrin),Tempo (cyfluthrin), DeltaGard (deltame-thrin) and Scimitar (lambda-cyhalothrin),are labeled for ant control on golf courses.The best time for applying pyrethroidsis early in the growing season, soon afterthe mounds appear. At that time,new colonies are just getting started, andestablished ones are weakened from over-wintering, with depleted food reserves, olderworkers and few new brood. Such treat-ments often provide 50%-70% suppressionof mounding for four to six weeks, althoughthey are unlikely to totally eliminate the antsor mounds.

Chipco Choice and TopChoice granularinsecticides, which contain the active ingre-dient fipronil, are labeled against mole crick-ets, fire ants and nuisance ants on Southern

Root aphid distribution

GCM 89November2006

Literature cited1. Lopez, R., and D.A. Potter. 2000. Ant predation on

eggs and larvae of the black cutworm. (Lepidop-tera: Noctuidae) and the Japanese beetle (Cole-optera: Scarabaeidae) in turfgrass. EnvironmentalEntomology 29: 116-125.

2. Lopez R., D.W. Held and D.A. Potter. 2000. Man-agement of a mound-building ant, Lasius neonigerEmery, on golf putting greens using delayed actionbaits or fipronil. Crop Science 40: 511-517.

3. Maier, R.M., and D.A. Potter. 2005. Factors affectingdistribution of the mound-building ant Lasius neoni-ger(Hymenoptera: Formicidae) and implications formanagement on golf course putting greens. Journalof Economic Entomology 98:891-897.

4. Maier, R.M., and D.A. Potter. 2006. Seasonalmounding, colony development, and control ofnuptial queens of the ant Lasius neoniger. AppliedTurfgrass Science May 2005. Online: doi:10.1094/ATS-2005-0502-01-RS.

Daniel A. Potter (dapotter@uky.edu) is a professor ofentomology at the University of Kentucky, Lexington. ReidMaier, his former graduate assistant, received a master'sdegree in entomology in 2004.

may have value as part of an overall ant man-agement plan.

RecommendationsMuch remains to be learned about the

biology and management of mound-buildingants on golf courses. For example, althoughgreens constructed according to recommen-dations with a root-zone mix high in sandseem unsuited for permanent nests, we donot know if push-up greens are suitable nest-ing sites. If they are, ant mounds would beexpected to be more uniformly distributedthroughout such greens.

In summary, our research indicates thatmultiple factors contribute to ant moundsbeing concentrated around the edges of sand-based putting greens. Control measures shouldfocus on the perimeter, about 6 feet (2 meters)on either side of - and including - the col-lar, whether baits or conventional insecticidesare used. This approach should help superin-tendents manage ants with reduced chemicalinputs. No one treatment is likely to eliminatea severe ant problem, but infestations oftencan be suppressed to tolerable levels using theapproaches described here.

~ The, urfgrass ant, ;usthatare a nuisance on golf cour

~ Controlling root aphids does not seemtoreduce or eliminate ants.~ Insecticides to suppress mounding are best applied early in the spring when the first

mounds appear.~ Timing insecticide applications to coincide with queen emergence and treating a

band just outside the collar of the green will kill some queens and prevent some futurenests.

~ Control measures should focus on the perimeter of the green, about 6 feet (2 meters)on either side of - and including - the collar, whether baits or conventional insecticidesare used.

FundingThis work was funded by grants from USGA and the

O.J. Noer Turfgrass Research Foundation.

AcknowledgmentsWe also thank the cooperating Kentucky superinten-

dents for allowing access to their golf courses: Jim Cox,CGCS, Arlington Golf Center, Richmond; Tim Hagerty,Cabin Brook Golf Club, Versailles; Mike Johnson, CGCS,Champion Trace Golf Club, Nicholasville; Nathan Hardin,Man 0' War Golf, Lexington; Melvin Johnson, Planta-tion Links, Nicholasville; Charles Griffith, Sweetbrier GolfCourse, Danville; and Mark Wilson, CGCS, Valhalla GolfClub, Louisville.

November 200690 GCM

golf courses. Fipronil is very effective against1. neoniger and can provide season-long sup-pression of mounding (2). One reason it isso effective is that its relatively slow knock-down activity allows exposed workers timeto return to the nest, where the insecticide isspread among nest-mates by mutual groom-ing. At present, fipronil is labeled only in the13 Southern states where fire ants are estab-lished and therefore is not an option for useon temperate-zone golf courses.

Spot-treating with MaxForce Fine Gran-ule Insect Bait (hydramethylnon) ofteneliminates small clusters of ant mounds ongreens (2). When the bait, which contains aslow-acting insecticide, is sprinkled aroundmounds, the workers take it into the nest andfeed it to the queen and her brood. Treatedsub nests usually become inactive within afew days, although it is uncertain how longit takes for the main nest to die out. Becauseants do not take wet bait, apply the bait afterdew dries and withhold irrigation for at least12 hours.

RESEARCH

Controlling root aphids and queensSome entomologists have suggested that

controlling root aphids with a soil insecticidewill indirectly suppress turfgrass ants. Wetested that approach by applying Merit 75WP (imidacloprid) at the highest label rateto creeping bentgrass tees with abundant antmounds. The treatment did not eliminate theroot aphids or reduce ant mounding withinsix weeks after treatment. Turfgrass antsobtain nutrients from diverse sources, andwe doubt that they are so dependent on rootaphid honeydew that controlling the aphidswould eliminate the ants.

We also tried intercepting newly emergedqueens with an insecticide in late summerbefore they could establish new nests. Wesprayed Kentucky bluegrass with DeltaGardat weekly intervals, then collected newlyemerged queens and placed them in thetreated plots. One-day-old and one-week-oldresidues killed 94% and 75% of the queens,respectively (4), but residual control declinedthereafter. Because queens emerge over abouta one-month span, several applications wouldbe needed to intercept most of them. Still, ifa superintendent treats for cutworms in latesummer, timing the application to coincidewith ant queen emergence and treating aband just outside the collar will kill queensand prevent some future nests. Such action