Velvety tree ants on the surface of a log (Liometopum occidentale). These nonaggressive ants have large populations, many homes and many queens.If all ants are not the same, then it follows that strategies used for ant control also must show variation.
Personnel in the pest management industry have long recognized the many species of ants that are considered structurally damaging or nuisance pests in the urban environment. The many species of ants found in and around structures differ in biology, behavior and morphology. Identification of the ant species attacking the structure is important so that the proper protocol can be developed and explained to clients/homeowners.
Most of these pest ants can be divided into three subfamilies: Formicinae, Myrmicinae and Dolichoderinae (see table on page 86). Ants within each of these groups share many traits in biology and behavior and hence may respond to similar control strategies.
TYPICAL ANT BEHAVIORS.
Some biological features will be common for all types of ants found in and around structures. For example, most ants will be foraging chiefly on the exterior of the structure at least during the foraging season, although this will vary with the shorter seasons occurring in northern latitudes.
Some ants will be opportunistic, feeding on the interior if food is available, especially when weather is not conducive to exterior foraging. Ants seek shelter in structures either as nesting sites or because of weather conditions. Vegetation provides a major thoroughfare for ants to navigate between foraging arenas and structural interiors. Working with the clients or homeowners to eliminate tree branches, shrubs or other vegetation in contact with the structure should be a primary line of defense.
Solving other structural problems such as eliminating wood that is in contact with soil, general yard sanitation by removal of unnecessary wood and debris, and proper drainage are additional general measures that will assist in solving ant problems. Special attention should also be made to timbers or wood used in landscaping, wood fencing in contact with structures, and the slope and attachment of patios and decks. These may provide either nesting sites or transit avenues for ants. Correction of these problems requires the cooperation and education of the homeowner or client. An integrated approach to ant problems has long been recognized incorporating these cultural procedures with chemical applications.
After following the previous guidelines, solutions to ant problems generally fall into two broad categories: Some ants can be controlled, while other ants can be managed. Identification of the ant species is imperative to determine which approach will be successful.
Consideration of only a few major ant pests are considered here but hopefully these guidelines and suggestions will be helpful for personnel to develop specific protocols for the ants and conditions in their localities.
WHEN TO MANAGE.
Management is the best solution for ant colonies with large populations, many queens (polygynous), many homes (polydomous), and that do not display aggression to workers from other nests. This last feature is also described as the ants being unicolonial and refers to the free flow of workers between nests and/or having no distinct boundaries between colonies. Common structure-infesting ants in this category (the dolichoderine group) include odorous house ants (Tapinoma sessile), velvety tree ants (Liometopum spp.) and Argentine ants (Linepithema humile).
These ants are non-stinging, have a single node, possess a slit-like opening at the base of the gaster and release chemical defenses in the form of repugnant volatile odors.
Management of these ants can be achieved with monthly or regularly scheduled service during peak seasons of activity. Baiting with gels, liquids or granules plus spraying, or a combination of these tools is usually necessary. Regular service should include a thorough inspection, as these ants will readily move from one site to another and may be infesting several residences.
During dormant seasons when the ants are confined to the interior, treatments and inspections may be more sporadic as the ants forage for water or food. Baiting may be successful in eliminating the ants when the ants are confined to the interior of the structure. These periods may occur because of temperature variations within structures. Establishing a rapport with clients is a fundamental part of a management protocol. Ants will often reinvade the structure because these ants are polydomous (have many homes), and colony fragments containing queens will readily re-enter and re-establish nests within structures; hence a management protocol is most successful.
Argentine ants (Klotz et al. 2010) can be used as a model to understand the biology and management of the related species of velvety tree ants and odorous house ants. Their nonaggressive behavior and ability to nest in nearly any location and to readily move their nests require this management approach. In investigating any of these dolichoderine ants, many different nesting sites can often be found around one structure. Furthermore, inspections on subsequent days typically reveal that these nesting sites will have been moved. Permanent nesting sites do not exist, as workers with brood and even a queen or two will nest under a board, pile of leaves, a pipe, a piece of metal or whatever is available around the structure. Baiting at entry points to the structure and on the interior may be effective and will require scheduled maintenance. Combination of an exterior perimeter spray with baits on the interior and/or the exterior may also be effective. Continual monitoring with inspections will determine the necessity of chemical reapplication.
WHEN TO CONTROL.
Conversely, control or elimination of the colony follows the protocol of finding the nest when dealing with ants that set up permanent and well-established nests. Colonies of these ants may have single or multiple queens and will show aggression toward other ant species and ants from different colonies of their own species. Their homes are more defined and more permanent. These ants include the formicine ants (one-node, nonstinging) and some of the myrmicine (two-node, stinging) ants. Pest ants in these categories include carpenter ants, cornfield or moisture ants, pavement ants and pharaoh ants.
Control based on finding the nest is particularly effective with single-queen colonies such as carpenter ants. These colonies are known for establishing their parent nest on the exterior of the structure in buried wood, a stump, the heartwood of a living tree or landscaping timbers. Satellite nests are established within structures in attics, under subfloor insulation and in voids. Both parent and satellite nests can be eliminated by baiting and/or with the application of perimeter sprays. Baits, sprays and dusts that are transferred throughout the colony by contact through grooming or trophallaxis (shared food) will eliminate the workers and subsequently the colony.
This find-the-nest protocol is followed by either application of a toxicant directly to the nests (parent and satellites) or by utilizing the workers to transfer the toxicant to the remainder of their nestmates by means of bait or by transfer of sprayed material.
Ant colonies with many queens (polygynous) found in the subfamilies Formicinae and Myrmicinae have a closed social system and are aggressive to other ant species and to ants from other colonies. Their typical ant behavior of exchanging food and grooming within the colony is advantageous to this control objective, since chemicals applied on or near these nests are spread through the colony and it is eliminated. If the colony is large and well-established, follow-up may be required in the form of inspections and additional chemical application of baits and/or sprays.
A STARTING POINT.
Identification of the pest ant is the first step in deciding whether a management or control protocol will be most effective. For further assistance, check the references listed at right, local extension personnel who have been trained in ant identification and trusted Internet resources. Species of ants, foraging seasons and size of colonies will differ in the various habitats where ants are problematic. Develop appropriate protocols for the species in your area.
Baiting Study Shows Promise Against Stubborn Ant Species
Ray Meyers has lived in Florida for more than 50 years; he loves the sun, the coastline and the arts and culture. The only thing he doesn’t like is the ants. Ants are pervasive in Florida, and while they may be small, they can cause quite a large hassle for pest management professionals.
As president of Pro-Line Professional Service based in DeLand, Fla., Meyers serves both residential and commercial accounts across Central Florida. The most notorious species he sees in his territory are crazy, Argentine and acrobat ants. “Ant control brings me the most business, but it’s also where I lose the most business, because these ants can be so hard to control,” he says. With such invasive species, Meyers often has to send his technicians back to conduct retreats, which can be just as expensive as the original service once you factor in product, labor and operational costs.
In August 2010, Meyers began participating in a study with Bayer Environmental Science, using Maxforce Quantum Ant Bait in addition to his standard perimeter treatment for both residential and commercial accounts. Meyers has been running two routes for the study: one with his standard residual spray application, and the other placing Quantum baits around the perimeter in addition to his standard application. The test runs through August 2011, but Meyers has already seen a 35-percent reduction in callbacks on the Quantum route.
Meyers says he’s happy with the results so far. “Reducing callbacks not only saves labor and vehicle costs, but also prevents the potential loss of a customer. My technician is happy as well because he knows his work is actually affecting the ants. Plus, he’s doing less running around to fix a problem he thought was already under control.”
Source: Bayer Environmental Science, www.backedbybayer.com
Hedges, S. A. 2010. Field guide for the management of structure-infesting ants. 3rd ed. Cleveland, Ohio: Franzak and Foster.
Klotz, J., L. Hansen, R. Pospischil, and M. Rust. 2008. Urban ants of North America and Europe: Identification, biology, and management. Ithaca, N.Y.: Cornell University Press.
Klotz, J., L. Hansen, H. Field, M. Rust, D. Oi, K. Kupfer. 2010. Urban Pest Management of Ants in California. University of California Agriculture and Natural Resources Pub. 3524.
Klotz, J. 2004. Chapter 11. Ants. In Handbook of Pest Control. 9th ed., pp. 634-693. Cleveland, Ohio: Mallis Handbook and Technical Training Co.
Smith, M.R. 1965. House-infesting ants of the eastern United States: their recognition, biology, and economic importance. Agric. Tech. Bull. 1326. Washington, D.C.: U.S. Dept. Agriculture, Agricultural Research Service.
Photos courtesy of Laurel Hansen. The author is professor at Spokane Falls Community College. Contact her at firstname.lastname@example.org.