Updated: Sep 30, 2020
When trying to control red imported fire ants, one of the most insidious hazards to turfgrass and agricultural crops in the southern United States, the Texas two-step approach is a good one. This methodology relies on a broadcast insecticide bait treatment, as well as a topical application of a drench or other insecticide to the mound itself. That, along with some cultural practices that reduce the chance of infestation, will actually control these pests—to a degree.
“What we promote is the IPM approach,” says Bastiaan “Bart” Drees, professor of entomology and extension specialist in the department of entomology at Texas A&M University in College Station. He’s studied fire ants since coming to the state over two decades ago and has written the book “A Field Guide to Common Texas Insects.” He says that any horticultural entomologist in eastern Texas will inevitably have to undertake a study of fire ants out of necessity. These ants were introduced from South America into Mobile, Ala., in the 1930s. Texas has such a problem that the university set up the Texas Imported Fire Ant Research and Management Project to cope with the issue.
Control measures will almost certainly be needed once they infest a landscaped area, Drees says. The two-step method developed at Texas A&M is based on the premise that an ant bait insecticide broadcast over the entire lawn or turf grass area, followed by an application of a drench, granule, dust or another bait insecticide specifically to undesirable ant mounds, will provide ant-free grass. The localized mound treatments can be made between broadcast bait treatments, if necessary. They will not eliminate the pest, however, because reinvasion will almost certainly occur over time. This is particularly true if the grass is adjacent to untreated ant-infested areas.
Otherwise, the red imported fire ant can be distinguished by its small size, from 1/8 to .25 inch, and with a lot of variation among individual sterile female workers. They are reddish brown with black abdomens, and when disturbed, they are fast movers. There can be up to half a million ants in a nest. Often, they are distinguished by the distinctive mounds they build in grass, though Drees emphasizes that in certain soil types they may not build mounds at all.
“This ant is highly attracted to water,” Drees says. Thus, one of the means of avoiding infestation is to make sure there are no standing pools of water or irrigation leaks around lawns or sports facilities. They also love to chew on electrical insulation, so facility managers should keep an eye out around these installations and protect them. The ants seem to avoid xeriscape and pea gravel if possible, and are less likely to infest areas where honeydew-producing aphids are not infesting landscape plants, though they can survive under the most desolate conditions if necessary.
Control measures will almost certainly be needed once they infest a landscaped area, Drees says. The two-step method developed at Texas A&M is based on the premise that an ant bait insecticide broadcast over the entire lawn or turfgrass area, followed by an application of a drench, granule, dust or another bait insecticide specifically to undesirable ant mounds, will provide ant-free grass. The localized mound treatments can be made between broadcast bait treatments, if necessary. They will not eliminate the pest, however, because reinvasion will almost certainly occur over time. This is particularly true if the grass is adjacent to untreated ant-infested areas.
Bait insecticides are readily available to professional turf managers. These are corn and soybean-based products of various types impregnated with insect growth regulators and other active ingredients such as metabolic inhibitors. These are the ones recommended for use in Texas: indoxacarb (Advion), which can give 90 percent control within a week or so; hydramethylnon (AmdroPro, Maxforce and Probait), which may take up to six weeks to control ants, with higher rates acting faster; abamectin (Ascend, Clinch or Advance), which can take months to be efficacious, but is very safe for the environment; fenoxycarb (Award), also very slow-acting, but safe and cheap; pyriproxyfen (Distance and Esteem), long-lasting, cheap and safe; and s-methoprene (Extinguish), slow-acting, but very safe.
Texas A&M recommends that bait be kept dry for maximum ant palatability. Hand or chest spreaders may be used for small areas such as lawns, but larger areas may require equipment such as an electric Herd seeder/spreader or even aerial application. Modifications to normal fixed-wing aerial seeders are recommended, and these guidelines can be found, along with other information on fire ants, at the TIFARMP Web site, fireant.tamu.edu.
A non-bait product that can also be broadcast-applied is granular fipronil (TopChoice), which is expensive, but acts rather quickly and has a true residual effect. Control takes place within four to eight weeks and can last through the ant season. Drees notes that this is a “near-absolute” control that must be watered in, but can be applied in any season. The true baits are used most effectively when ants are foraging, particularly in late summer and fall, and may require more than one application per year to maintain maximum control.
The second part of the two-step program encompasses mound follow-up applications of other insecticides. That may be another mound application of a fast-acting bait, a granular product watered in after application, or a powder, such as acephate (Orthene or many others). Liquid mound drenches are also used. These include the plant-derived products containing pyrethins in many brands, often formulated with diatomaceous earth and a surfactant. Derivatives of pyrethrins and pyrethroids, again under many brand names, are also effective applied as drenches, dusts or granules. Spinosad products formulated as a wettable powder, liquid drench and bait are effective and certified as organic by the Organic Materials Research Institute. Check the label for ingredients. Many such products can be purchased over the counter in unrestricted formulations.
Many home remedies have been tried and reported by desperate grass managers, but many of these are not effective, Drees says. One of the oldest of these remedies is one that can work: Boiling water can be effective when poured on the mound. The treatment kills grass, but will eliminate mounds about 60 percent of the time.
Drees says that the chances of reinfestation are greatly reduced when a communitywide control program is instituted. This can be coordinated on a local basis by groups such as homeowner associations, and on a larger basis by county or municipal governments. He says it makes sense for a turfgrass manager to look for help in the neighborhood for a species that is this mobile. These should include follow-up checks and the cooperation of homeowners and businessmen in the control area. In the end, such a program can reduce injuries from fire ants, as well as reduce overall cost of treatment.
One of the very promising elements of red imported fire ant control is the use of several parasitic phorid flies from South America that are being introduced, to different degrees, in Southeastern states. Biological control agents, these species of flies are being produced and distributed by the USDA Agricultural Research Service and the University of Texas at Austin. Drees notes that a turf manager can’t purchase these flies, which are being released selectively on a regional basis, but might be able to contact his land grant university and ask to have his area included in the release program.
Fire ant-specific diseases are also being released in some areas by USDA, with the U.S. Fish and Wildlife Service consulting. These include a microsporidium that causes colony decline. Other diseases that might affect fire ants are being used experimentally, including viruses and a fungus. Drees says that the presence of these diseases may have helped reduce populations in Texas, assisted by drought conditions that appear to make the diseases more effective. Other biocontrol candidates are also being examined, and those interested in reading more about the work at ARS can go to www.ars.usda.gov. The agency also provides maps showing quarantined areas.