The Türfgrass neoniger

By Sean F. Werle, University of and this number is probably a good estima- Massachusetts, Amherst tor of the diversity in any temperate area. Ant diversity will increase with decreasing hat are ? This question has latitude — the closer to the equator one almost as many answers as there looks, the more species of ants one can find. are people who might consider it. WTo your child, ants may be the industri- ous residents of an antfarm on a bookshelf Why Ants Succeed or the fascinating combatants that engage in The reasons for the evolutionary success epic battles on the pavement of your drive- of ants are numerous, but there are several way. To an ecologist, they are members of that stand out. These are eusociality, chem- the family Formicidae, and are one of ical adaptation and general hardiness, prob- the most important cogs in the complex ably in that order of importance. biological machinery that Eusociality refers to the fact that ants are they study, exerting an effect social , similar to some of the bees and The pest status of ants on every other part of a given wasps. E.O. Wilson defines eusocial insects is a phenomenon ecosystem. as those that possess three traits: cooperative If one is in the business of brood care, reproductive caste differentia- that has developed managing turf however, ants tion and overlapping generations. fairly recently; within are more and more often All ants exhibit these traits. Immature becoming a problem that has ants are completely helpless and depend the last 20 to 30 years. to be dealt with. The pest upon adult "worker" ants to care for and status of ants is a phenome- feed them. These worker ants are incapable non that has developed fairly of reproducing; that is the job of the repro- recently, within the last 20 to 30 years. The ductive castes, which include the queen, or reasons are not quite clear, but some queens, and the winged males. hypotheses have been advanced and this Ant colonies can be monogyne, with article will address those ideas and also try only one queen, or polygyne, with multiple to answer the question posed above. queens. Both of these conditions can occur in the same species, as is the case with Solenopsis invicta, the , The Ant World a notorious ant pest that is discussed in It has been said that the combined num- another article in this issue. ber of ants on the Earth is greater than all "Overlapping generations" refers to the other land combined, which is fact that ant queens survive for many sea- quite possible. Studies of the turfgrass ant, sons, and thus can produce many genera- Lasius neoniger, reveal populations greater tions of offspring in a lifetime. Wilson had a than 10 million ants per acre in heavily turfgrass ant colony that lived for 30 years infested turf. A single ant colony can have as with a single queen. few as 35 ants, in some species, to as many The extreme chemical adaptation of as 1 million or more in others. ants is another factor in their success. Ants There are over 12,000 described species have evolved many glands to produce of ants; a large proportion of these are trop- chemicals that help the colony function. ical, but there are many temperate and even Some are used to raise an alarm in the case arctic species. The state of Massachusetts is of danger from outside, some are for mak- home to approximately 110 species of ants, ing trails that other ants can follow to a source of food or water and still others are Lasius neoniger, the egg-laying queen spends antiseptic, keeping the colony free of infec- most of the season laying fertilized eggs that tions caused by fungi or bacteria. This will develop into female worker ants. These extreme chemical dependence has given workers comprise the majority of the ants a highly developed sensitivity to many colony and are responsible for all of the chemical compounds and some studies food gathering, defense and have shown that they are capable of detect- brood care for the nest. Many ing and avoiding insecticide applications ants share food within the Late in the summer, (Vittum and Werle, unpublished data). colony through a process The general hardiness of ants is quite called trophalaxis where liq- the queen begins to lay remarkable. Some are able to survive immer- uid food is regurgitated and fertilized eggs. Once sion in water for as long as two weeks and passed between workers or others have been exposed to intense radia- from workers to the queen or hatched, specially tion with no ill effect. This toughness means the brood (larvae). treated larvae develop that, for many species, an established colony Late in the summer, the is unassailable by other insects or animals. queen begins to lay fertilized into large winged Many ants can both bite and sting, and eggs and also to feed some of females called Alates; are very capable defenders of their colony. her female larvae differently The tropical ant (Paraponera clavata), from than normal worker larvae. The who will become Central and South America, is commonly unfertilized eggs develop into queens once they mate known as the bullet ant because it is said winged male ants and the spe- that the sting of this ant is more painful than cially treated larvae develop during a nuptial flight, a gunshot wound, though the accuracy of into large winged females. usually in August. this is debatable. These winged ants, called alates, build up in the nest and are prevented from leaving by the workers. Colony Life Cycle Sometime near the end of August, some poor- The life cycle of a colony is roughly sim- ly understood signal causes the workers to ilar for all ant species. In the turfgrass ant, allow the alates out of the nest and they take

Turfgrass Ants and Predatory Beetles in Pitfall Traps m

Ants Beetles

45 feet 30 feet 15 feet Border 15 feet 30 feat 45 feet Fairway Rough flight simultaneously across large regions. This These ants need grasses in order to sur- is called the nuptial flight and it occurs once vive because a large part of their food is every year. During this flight the male and indirectly derived from the grass itself. The female ants mate and, after flying some dis- ants don't consume plant material; instead, tance, settle back to the ground. they tend small [Anuraphis maidi- The males have served their radicis, the corn root ), which feed on purpose at this point and are the grass roots and produce a sugar-rich The ants don't doomed, falling prey to other excretion called honeydew which the ants ants or insects or dying of consume. These aphids, in turn, are com- consume plant starvation. The females, now pletely dependent on the ants. material, instead they mated and ready to establish Metcalf described this relationship as new colonies, will fly in follows: "This aphid is rarely found on roots tend small aphids search of an open grassy area. except where attended by the ants and, if which feed on the grass Studies have shown that the placed on the surface of the ground, is queens will avoid entering apparently helpless so far as finding a place roots and produce a wooded areas. Thus, if they to feed is concerned. An ant finding one of sugar-rich excretion, began their flight on a golf these aphids, however, immediately picks it course, they will likely up, carries it underground and places it on called honeydew, remain somewhere on the the roots of one of the aphid's food plants." which the ants course. Once they have In the winter, the ants bring the eggs of found a suitable spot, they the aphid down below the frost line and in consume. will chew off their wings, the spring they place the newly hatched burrow into the ground and aphids back on the roots of the grass. The lay a small clutch of eggs. root zone of ant-infested turf often sup- These eggs develop into undersized work- ports large populations of these aphids, ers called nanitics that immediately begin though seldom enough to cause pathology foraging. Once they have brought back in the plant. enough food, the queen begins laying eggs In addition to this food source, the ants that have enough energy to develop into constantly forage around the nest, preying normal workers. upon other insects and insect eggs. Rolando Despite the ant's reputation for organi- Lopez, a scientist working at the University zation, this whole process is actually rarely of Kentucky, has observed turfgrass ants car- successful. There are many dangers faced by rying away black cutworm eggs. This obser- the foundling queen and her tiny nanitic vation has implications in regard to control workers. But, when she does succeed, a new because it suggests that if ants are com- colony is established. Given the large num- pletely eradicated from an area, secondary bers of alates produced every year, the num- pest outbreaks could result. ber of ant colonies in an area will tend to Turfgrass ants also cause a significant increase over time. amount of soil aeration and their activities move nutrients down below the thatch; activities that can be beneficial to the health Ants as Turfgrass Pests of the turf ecosystem. As turfgrass pests, all of this evolutionary The primary problem with turfgrass ant success can add up to a big thorn in the turf- activity in managed turf is their nest struc- grass manager's side. In New England, the ture. The ants nest in the soil in large com- primary ant problems are caused by the plexes of interconnected tunnels and gal- aforementioned turfgrass ant, Lasius leries that can extend more than three feet neoniger. This is a small light to dark brown into the soil and often have multiple ant, about an eighth of an inch long, which entrances. primarily inhabits open areas such as turf, cornfields and pastures. The ants nest in the soil in large com- plexes of interconnected tunnels and gal- leries that can extend more than three feet into the soil and often have multiple entrances. All of the soil excavated to form these tunnels is brought to the surface. The result is an "anthill" like structure. It is not an ant mound in which the ants actually reside. In an infested area there can be as many as ten of these small ejected mate- rial mounds per square yard.

Anthills and Mounds All of the soil excavated to form these tunnels and galleries is brought to the sur- face and piled around the entrance holes leading into the nest. The result is an on golf course greens, they can detrimental- "anthill" like structure. This term is enclosed ly affect game play, a situation that most in quotes to emphasize the distinction members will find unacceptable. After between an anthill or ant mound in which some time, the small piles of soil will smoth- the ants actually reside, and an anthill which er the grass underneath, resulting in small is simply composed of material ejected dead patches that remain even after the ants from beneath the soil by the ants such as have ceased using that entrance. those constructed by turfgrass ants. In an The most pressing concern, however, is infested area there can be as many as ten of the damage to equipment that results from these small ejected material mounds per mowing over the mounds. The small soil square yard and this causes a number of particles dull mower blades and clog rollers, problems. causing a significant increase in equipment Aesthetically anthills and mounds can maintenance costs. greatly degrade the appearance of turf and, Why ants increase western Massachusetts), timing of applica- tion can be an important factor in control. Among a number of possible causes for If an effective material is applied at this the recent increase of ants as turf pests, the time, the colony will suffer a serious setback two that stand out are decreased mowing in its initiation of warm weather activity height and the loss of organochlorine insec- and this can delay the onset of turf man- ticides. For many years, chlorinated organic agement problems. compounds such as chlordane were used Another possible avenue of control is to extensively in turf to control a number of adjust mowing height in order to mask ant pests, mainly scarab beetles. These com- activity. Fairways mowed at three quarters pounds are highly toxic to ants of an inch are unlikely to exhibit ant prob- and thus ant populations were lems because the soil ejected from the nests The best long-term probably secondarily con- will not reach above the grass. Often solution is probably to trolled by these applications. changes such as this are unacceptable to Since the use of these materi- club memberships and so ants remain a dif- find ways to coexist als was discontinued in the ficult and expensive problem for the people 1970s, ants have possibly been in charge of managing turf. with the ants, using a released from this chemical combination of care- constraint and thus are able to Conclusion fully timed pesticide emerge as pests. Another possibility is the It is appropriate to return to the ques- applications and "Stimpmeter factor." As golf tion posed at the beginning: what are ants? adjustments to fairway courses have competed to Hopefully the point has been made that increase green speed, mowing while ants are a serious problem in many and greens mowing heights have steadily de- turfgrass settings, they are beneficial in heights. creased. Turfgrass ants are sel- other ways also. dom cited as home lawn pests Understanding what ants are and how and their presence is difficult they fit into the local turf ecosystem (i.e., to detect in a golf course rough. This is identifying and controlling food sources) is because the grass is mowed at a height that important for responsible ant management. masks ant activity. On short-mowed fair- However, if all your efforts prove fruitless, ways and greens, this masking is removed then the best long-term solution is probably and ants that may have been present but for turf managers to find ways to coexist undetected at a slightly higher mowing with the ants, using a combination of care- height are revealed as pests. fully timed pesticide applications and adjustments to fairway and greens mowing heights. Controlling Turfgrass Ants Think of it this way: With all of the myr- Lasius neoniger has proven difficult to iad insects out there that eat grass, can control. Many insecticides are ineffective insects that eat other insects be all that bad? against them and, as mentioned before, they are capable of detecting applications and Sean F. Werle is a graduate student of Dr. avoiding materials in some cases. Studies at Pat Vittum in the Department of Entomology Dr. Vittum's lab at the University of Mass- at the University of Massachusetts, Amherst. achusetts have revealed no material that is effective for more than a few weeks in con- trolling mound-building activity. Some patterns have been seen that may be helpful, however. Since the ants spend the winter deep in the soil and move rapid- ly to the surface in the spring (early April in