Managing
Red Imported Fire Ants
in Urban Areas

*Professor and Extension Entomologist, Extension Associate, Professor--Departmentof Entomology, Professor--Department of Entomology, Associate Professorand Extension Urban Entomologist, The Texas A&M University System;and Coordinator for Plant Quality Programs, Texas Department of Agriculture. 

The red imported fire ant is a nuisance and its sting can cause medicalproblems. Fire ants can interfere with outdoor activities and harm wildlife.Ant mounds are unsightly and may reduce land values. In heavily infestedareas, eliminating fire ants is highly desirable. However, eradicationof this species is not currently feasible (see History and Control Efforts,p. 17). Insecticides are not always 100 percent effective, nor are theyapproved for use everywhere the ants occur.
They are also expensive and potentially hazardous to the environmentand other animals. Chemicals provide only temporary control of fire antsand must be reapplied periodically. When deciding whether or not to controlfire ants, one must weigh the benefits of fire ant control against
the cost and environmental impact of control methods.

Integrated Pest Management (IPM). This bulletin describessite-specific, goal-oriented management programs for common urban siteswhere fire ants occur. Where applicable, you should select programs thatuse a combination of non-chemical and chemical methods that are effective,economical and least harmful to the environment. The goal of fire ant managementis to prevent or eliminate problems caused by unacceptably high numbersof fire ants, rather than to eliminate ants from the ecosystem.

USDA Quarantine Program. Because fire ants are easilytransported in nursery stock and soil, the United States Department ofAgriculture (USDA) developed a quarantine program for this pest in the1950s. In Texas, the USDA Imported Fire Ant Quarantine program is administeredby the Texas Department of Agriculture (TDA). This quarantine is designedto minimize the spread of imported fire ants by requiring proper inspectionand treatment of all nursery stock, turfgrass, hay and other articles shippedout of quarantined Texas counties (Fig. 1, p. 8). TDA inspectors also surveynon-quarantined counties for fire ants and occasionally treat small, isolatedinfestations.

Management Options

Following are options for managing various kinds of fire ant problems.When using pesticides, use only products labelled for the location or "site"you want to treat. For instance, DO NOT use a product in your vegetablegarden unless that site is listed. Many combinations of control optionsare available, and there may be no single best method. The following suggestionsare not intended to preclude other effective methods.
 

Treatment options

Program 1 - The "Two-Step Method": This program provideslong-term ant suppression in ornamental turf and non-agricultural lands,including roadsides. It is best suited to medium-sized or large areas,and the cost is moderate. This approach is not suggested for previouslyuntreated areas with large numbers of native ants and few fire ant mounds(15 to 20 per acre or fewer). The goal of this program is to minimize theuse of individual mound treatments. Note: This program is also suitablefor pasture and rangeland, provided that the products selected are specificallyregistered for use in these sites.

1. Make an annual or semi-annual broadcast application of a bait-formulatedinsecticide, or use an outdoor bait station product as directed. Conventionalbaits are applied at a rate of 1 to 1 1/2 pounds of product per acre. Periodicbroadcast applications of fire ant baits provide roughly 90 percent suppressionof ants when properly applied. A bait can be broadcast using hand-held,vehicle-mounted or aerial applicators. The speed and duration of ant suppressiondiffer with the product used. Hydramethylnon bait (see Table 1, p. 18 fortrade names) provides maximum control 3 to 5 weeks after application, whilefenoxycarb bait provides maximum suppression 4 to 9 months after treatmentdepending on environmental conditions. Using higher rates of fenoxycarbbait does not eliminate colonies more quickly. Late summer applicationproduces maximum suppression the following spring. Where there are manymounds per acre (200 or more), a second application after the maximum effectsof the first treatment have occurred may be needed, since not all moundsare affected by a single bait application.

2. Wait several days after bait is applied, and then treat nuisanceant colonies (such as those in sensitive or high traffic areas) using anindividual mound treatment method (see Program 2, Step 1, below). Otherwise,be patient and wait for the bait treatment to work. Any nuisance moundsthat escaped the effects of the bait treatment or colonies migrating intotreated areas should be treated.

Repeat the bait application whenever ants reinvade the area and moundnumbers reach about 20 to 30 per acre. Bait products do not protect againstreinvasion by ant colonies from surrounding land or by newly mated queens.Ant populations can fully recover within 12 to 18 months of the last treatment.Low-lying, flood-prone areas are more prone to reinfestation.

Program 2 - Individual Mound Treatments: This approachis best used in small areas of ornamental turf (usually 1 acre or less)where there are fewer than 20 to 30 mounds per acre or where preservationof native ants is desired (Fig. 2, p. 15). This program selectively controlsfire ants, but reinvasion should be anticipated. It generally requiresmore labor and monitoring than other programs, and is not suggested forheavily infested areas.

1. Treat unwanted fire ant mounds using the individual mound treatmentof choice. These are applied as dusts, granules, granules drenched withwater after application, liquid drenches, baits, or aerosol injections.Home remedies such as very hot water mound drenches also may be used.

2. Continue treating undesirable mounds that appear, as needed.

Program 3 - The "Ant Elimination Method": This programeliminates nearly all ants in treated areas. Its effects are more rapidthan those of other programs, and reinvasion of treated areas by migratingcolonies and mated queen ants is minimized as long as the contact insecticideremains effective. However, it is more expensive and uses more insecticide.This approach is frequently used by commercial applicators.

1. (Optional). Broadcast a bait-formulated insecticide in areas wherethere are many mounds (more than 20 per acre), or individually treat fireant mounds. Wait 2 to 3 days after applying a bait before conducting thenext step.

2. Apply a contact insecticide (see Table 1, p. 18) to turfgrass every4 to 8 weeks, or when ant activity is detected. Liquid or granular productsthat can be evenly applied to an area are appropriate for this. Some productlabels instruct the user to spray "ant hills." Although initial surfacetreatment may not eliminate ants located deep in mounds,
routine reapplication will eventually eliminate colonies.

Program combinations: Any of the three programs can beused on specific sites within a managed area where different levels offire ant control are desired. On golf courses, for instance, Program 3might be suitable for high use areas such as putting greens and tee boxes.In fairways and rough areas, Program 1 may be sufficient.

Treatment options

* If ants are entering or could enter the home from outdoor colonies,treat mounds near the building using one of the programs described forHome Lawns and Other Ornamental Turf Areas. A contact insecticide witha long residual, such as chlorpyrifos, diazinon or a pyrethroid, also canbe applied as an outside barrier around the base of the structure. Caulkingcracks and crevices also may help prevent ant entry.

* If fire ants are foraging indoors, use a bait labelled for indooruse as directed. Examples are baits such as abamectin (PT 370-Ascend^®)or bait stations containing hydramethylnon (MaxForce^®,Combat^®)or sulfonamide (Raid^® Max). Fire ant baits eliminate thecolony. Bait products not specifically registered for fire ant controlmay or may not control them. Alternatively, treat ant trails or infestedareas with contact insecticide products registered for such use (see Extensionpublication L-2061, "House Infesting Ants").

* Follow trails of foraging ants to find colonies located indoors andtreat them with contact insecticide dusts or sprays (containing chlorpyrifos,pyrethroids and others) injected into the nest.

Note: For safety reasons, an electrician or a licensed pest controloperator should treat infested electrical equipment. Specialized productsand training are necessary to treat these sites safely and effectively.

Treatment program

1. Turn off all electrical service before starting. With an individualmound treatment method, eliminate colonies around electrical and plumbingcasings and housings. Injectable aerosol products containing pyrethrins,or similar products, give immediate control. Hydramethylnon bait appliedto individual fire ant mounds will provide control in about 1 week, evenif the colony is located within the structure. Do not use liquid drenches,sprays, or products that may damage insulation around electrical fixtures.Treatment of a larger area around the electrical structure is optional.Mound and area treatments are described in the section on Home Lawns andOther Ornamental Turf Areas. Be extremely careful when applying pesticidearound water systems and well heads to prevent contamination of wells andground water. Once ants are eliminated, remove debris and soil to reducethe possibility of short circuits.

2. Treat the inside of equipment housings with products labelled forsuch use, such as State Fire Ant Killer with resmethrin, Rainbow InsectControl containing chlorpyrifos, Stutton^® JS 685 Powdercontaining synergized pyrethrins and silica gel, Ascend^®or Elastrel insecticide with dichlorvos.

Maintenance options

After ants are removed from the electrical equipment, prevent reinfestationand damage.

* Where possible, seal all sensitive electrical components, particularlythose that are not insulated. Examples are plastic housings containingcontact points of switches, relays and circuit breakers.

* Spray long-residual contact insecticides around housings, making sureto avoid the electrical equipment.

* Apply specifically labeled products to the housing itself (see Step2 in the treatment program above).
 

Treatment options

* Granular products containing carbaryl plus metaldehyde are registeredfor ants foraging in the garden. Products containing diazinon or chlorpyrifosare registered for soil insects in home gardens; they can be applied beforeplanting and may provide some temporary control of foraging fire ants.Follow all preharvest intervals indicated on the label when using a pesticideon and around food plants.

* Ant mounds can be shoveled out of the garden or treated with veryhot water, taking care not to disturb or treat the garden plants. Onlya few products containing pyrethrins or rotenone are registered for treatingfire ant mounds in vegetable gardens.

* Since most baits are not registered for use inside gardens, applybaits around the garden perimeter. Foraging ants from colonies both insideand outside the garden will collect the bait and take it to their colonies.

* To prevent ants from entering a garden, apply diazinon or chlorpyrifosspray or granules around the perimeter of the garden as a barrier, andtreat individual mounds near the garden as needed.

Organizing an Area-Wide Fire Ant Suppression Program

Fire ant management programs have been widely adopted and are successfulin many situations. However, because they are usually implemented by individuallandowners and managers, re-infestation from nearby untreated areas generallyoccurs. Most baits on the market today (e.g., Amdro^®,Award^®,Logic^®, Ascend^® and others) came from earlierefforts to develop products suitable for area-wide treatment programs,and are best suited for large-scale use.

Despite great public concern, neither the state nor federal governmentis currently planning or funding any large-scale fire ant treatment programs.It is up to local organizations to decide on the best IPM strategy fora particular situation. With the help of experts in the field, any groupcan organize an effective fire ant suppression program with or withoutthe help of a governmental agency.

The "Two-Step Method" (Program 1) for Home Lawns and Other OrnamentalTurf Areas is the method best suited for area-wide treatment. Homeownersand land managers may still need to treat a few mounds ("step two") betweenlarge-scale bait treatments, but far fewer than if no bait had been applied.

Matching the Program to Your Resources and Needs

There are many ways people can work together to conduct area-wide fireant suppression programs.

Coordinating neighborhood treatment. Homeowners can coordinatetreatment of their entire neighborhood each year, usually once in the falland once in the spring. Each homeowner should receive instructions on:1) appropriate fire ant bait products to purchase; 2) how to properly broadcasta bait; and 3) treatment date(s). Each homeowner is expected to make hisown applications or arrange for treatment on the designated treatment date(s).Contingency dates should be scheduled in case rain is forecast or the temperatureis less than 65 or greater than 95 degrees F on the primary treatment date.

Working through homeowner associations. Home-owner associationsmight contract with a local commercial applicator to broadcast fire antbait over the entire subdivision periodically, including common areas,medians and other community property in the area. They should be askedto evaluate the area and apply minor touch-up treatments as needed.

Working through city and county government. With enoughcitizen support, local governments can establish fire ant control programsthat both treat public areas and perhaps allow homeowners to have theirproperties treated for an additional fee. The municipal or county governmentcould contract with a commercial pest control applicator. Advertising shouldencourage entire blocks or neighborhoods to sign up, because the largerthe area treated, the longer lasting the control. Treatments would includeannual broadcast applications of a fire ant bait, follow-up checks andpossibly individual mound treatments as needed. The fee paid by individuallandowners could pay for the program.

It might be possible for a city government to coordinate the aerialapplication of a fire ant bait to an entire town. Smaller areas where baitscan't be applied, such as swimming pools and vegetable gardens, would haveto be covered during application. Widespread citizen support would be essential.The aerial applicators contracted by the city would have to agree to modifyequipment to apply the recommended amount of bait per acre, heed the FFAflying height over populated areas, and avoid bodies of water and agriculturalareas where food is produced. Many volunteers would be needed to successfullycoordinate and implement this program.

Szeged cheap hotelsPlanning to Ensure Success

Determine treatment areas. Some localized areas, evenwithin heavily-infested regions, have little or no fire ant infestation.Surveys should be conducted to determine if the number of red importedfire ant mounds is high enough to justify treatment.

Respect individual differences. Sensitivity to fire antsand to the use of insecticides varies dramatically from person to person.Some individuals might not want to participate in a control program becausethey believe fire ants are not a problem and serve useful purposes, orbecause they are opposed to using insecticides, natural or otherwise, ontheir property. At the other extreme are individuals who want no fire antson their property and don't care about the methods used to achieve thatgoal. Participation in an area-wide program should be voluntary or decidedupon through a democratic process.

Promote education and recognize limitations. The strengthsand limitations of the program should be acknowledged. For instance, abroadcast bait will eliminate most (usually 90 to 95 percent) of the fireant mounds in an area temporarily (6 to 18 months). It will not eradicatethem permanently. The speed at which suppression will occur is rather slow.Periodic, coordinated reapplication will be necessary to maintain control.Between broadcast treatments, some individual colonies may occur that requireindividual mound treatment. Landowners whose property borders untreatedareas such as agricultural lands, water edges, flood plains and wildernesswill likely have continuous migration of ant colonies onto their properties.

Follow pesticide laws and regulations. The StructuralPest Control (SPC) Board regulates the commercial use of insecticides inurban environments. SPC laws mandate that anyone applying insecticidesfor a fee be licensed by the Board and insured. Although you can applyinsecticides on your own property, you can not treat other yards in theneighborhood without a license.

Read and retain the insecticide product label. Those whouse insecticides must keep the label with the product. Never purchase alarge quantity of insecticide and re-package, divide, or store it in acontainer without the label. Always follow the directions on the product'slabel.

Take bids and review credentials. Before contracting witha commercial applicator company or private pest control operator, get severalbids based on the specific services you require. These firms must be licensedby the SPC Board.

Fire Ant Treatment Methods

Treatment methods and products vary greatly in effectiveness, speedof activity, practicality (labor requirements), toxicity to the user andthe environment, and cost. Carefully study available treatment methodsand their proper use in order to choose the best one for a particular situation.Many methods and products have been evaluated by research and Extensionfaculty. This information is available from county Extension agents andExtension entomologists. Per mound treatment costs range from about $0.15to more than $1.00 per mound, and bait treatments can cost $8.00 per acreor more.

Natural and biological control. A number of organismskill newly-mated fire ant queens. These include dragonflies, other ants,some types of birds, lizards, spiders and toads. Animals that eat ants,such as armadillos, may disturb mounds and eat some workers, but they arenot really useful in control.

Some parasites and pathogens are known to attack ants, and several havebeen marketed for fire ant control. The predatory straw-itch mite, Pyemotestritici (Lagreze-Fossat & Montane), that feeds on and paralyzesdeveloping fire ants is not effective when applied as directed and is potentiallyhazardous to the user. Parasitic nematodes (Steinernema spp.) areroundworms that seek out and enter insects, paralyzing them and developingin their bodies. Species and strains vary in their effectiveness. Strainstested to date caused ants in treated mounds to temporarily move away fromthe treated mound, but few colonies were actually eliminated. Parasiticfungi (Beuvaria bassiana) are also being evaluated as individualmound treatments. The most effective biological control organisms for large-scaleprograms will likely be those that spread from mound to mound. Severalare being evaluated for control, including flies, Strepsiptera and parasiticwasps.

It is hoped that introducing natural enemies of fire ants to the U.S.may someday help to control them, although natural enemies will not eliminatefire ants. In South America, where fire ants have many natural enemies,the ants are still present.

Currently, the best biological control method for fire ants is to preservenative ant species that compete with them (Fig. 2, p. 15). One way to preservenative ants is the judicious use of insecticides.

Physical and mechanical methods. Pouring very hot or boilingwater on a mound is a fairly effective treatment, particularly at timeswhen ants are close to the mound surface, such as on a cool, sunny morning.Approximately 3 gallons of hot water poured on each mound will eliminateabout 60 percent of the mounds treated. Be careful handling large volumesof hot water to prevent serious burns, and keep hot water off of desiredplants and grass.

Sometimes it may be sufficient to move colonies away from sensitiveareas such as gardens. Disturbing or knocking down mounds frequently willcause colonies to move. Some people believe shoveling one mound on topof another will force ants to kill each other, but this is not true.

Certain barriers can keep ants out of sensitive areas such as wood duckboxes or greenhouse benches. Talcum powder and Teflon-like tape or sprayproducts can be used on vertical surfaces, but lose their effectivenessin humid or damp conditions. Tanglefoot^®, a petroleum-basedsticky material available as a gel or aerosol, is effective temporarilyuntil it becomes coated with dust and other debris. Plates or wires heatedto about 140 degrees F form a hot barrier that ants will not cross.

Control devices. Various mechanical and electrical productshave been marketed for fire ant control. One device is designed to electrocutefire ant workers as they climb onto an electric grid inserted into themound. It will kill many worker ants, but the queens and brood are unaffected.There are vibrating and sound-producing units designed to repel colonies,and devices that use microwaves or explosive elements to heat mounds orblow them up. Such products are often marketed without scientific evaluation.The fact that a "control" device is on the market does not indicate thatit is effective. These products may kill some ants, but rarely eliminatea colony. Deceptive or fraudulent claims concerning fire ant control devicesshould be reported to the Texas Attorney General or the Federal Trade Commission.

Home remedies. In addition to very hot or boiling water,other "home remedies" have been tried. While these methods sometimes appearto work, they rarely eliminate colonies. Usually, the ant colony simplymoves to a new location, or the queen and a few workers temporarily remainhidden underground.

Gasoline and other petroleum products do kill fire ant colonies. However,petroleum products are dangerously flammable, kill grass and plants aroundthe treated mounds, and can seriously pollute the soil and ground water.Soap solutions, cleaning products or wood ashes soaked into the mound arebelieved to remove the protective oil coating from the ants. Use of batteryacids, bleaches or ammonia products can be dangerous and is strongly discouraged,except when they are ingredients in a registered pesticide product accompaniedby usage directions.

Sprinkling instant grits onto fire ant mounds is ineffective. In theory,the ants eat the grits, which then swell and rupture the ants' stomachs.In fact, only the last stage of the developing fire ant is known to ingestsolid food. All other life stages feed only on liquids or greasy materials.Some natural substances found in crushed or grated citrus peels are reportedto be toxic to fire ants. However, until proper formulations and applicationtechniques for these naturally-occurring chemicals are developed, theyare unlikely to be effective.

"Organic" insecticides. Several products said to be "organic"(of natural origin) are currently marketed for fire ant control (see Table1, Botanicals section, p. 18). All of these products are registered bythe Environmental Protection Agency as pesticides and some are very effective.They are not necessarily safer than other insecticides though, and shouldbe used with care.

Chemical control. Chemical insecticides (both "organic"and synthetic) continue to be the main method of battling fire ants. Insecticidesregistered by the Environmental Protection Agency pose minimal risk whenused as directed. Insecticide applications can be aimed at the foragingants and/or at the entire colony. Table 1 lists fire ant insecticides bygeneric names of ingredients. Carefully follow directions on the productlabel for the use of protective clothing, re-entry intervals, and wateringpractices before and after treatment.

Baits. Conventional bait formulations combine pesticide ingredientswith processed corn grit coated with soybean oil. Soybean oil is a feedingstimulant that is important to the bait's success. Baits can be appliedas spot treatments to individual mounds or broadcast over larger areas.To achieve satisfactory results:

* Use fresh bait, preferably from an unopened container or one whichhas been tightly resealed and stored for no more than 2 years. Purchaseonly enough bait to make one treatment and do not store large quantitiesonce the containers have been opened. Bait is only collected by ants whenit is fresh. It is then carried back to the colony and shared with othermembers of the colony. Rancid or stale bait smells bad and is ignored byforaging ants.

* Apply when worker ants are actively foraging. This can be determinedby leaving a small pile of bait in the area to be treated. When ants areseen actively removing the bait 10 to 30 minutes later, you will know boththat the bait is attractive and that ants are foraging. Tuna fish, petfood or potato chips are also attractive to foraging ants. Foraging activityslows when soil temperature is lower than 70 degrees F or higher than 95degrees F. In mid-summer, apply bait in late after- noon or early evening,since foraging ants are less active during the heat of the day.

* Apply when the ground and grass are dry and no rain is expected.

* Do not mix bait with other materials such as fertilizer or seed.

* Use appropriate application equipment and calibrate it properly. Differencesin the oiliness of bait brands and production batches can cause variationsin applicator output. Temperature and humidity also affect the rate atwhich bait flows through the applicator opening. The speed at which theapplicator is moving is an important factor, particularly with factory-calibratedsettings.

Hand-operated spreaders such as the Cyclone^® Seed Sower,Ortho^® Whirlybird, and Republic or Scott's Hand-held Spreaderare the least expensive applicators and are adequate for treating smallareas. The operator can walk or ride on the back of a vehicle. Some push-typeapplicators, such as Spyker^® Models 24 and 44, also maybe suitable, but some modification (attach fire ant plate) is requiredto keep from applying too much material. Most rotary and drop-type fertilizerspreaders will not apply fire ant baits at the recommended rate.

Electric spreaders such as the Herd^® Model GT-77A,Cyclone^®Spreader Model M-3 or similar applicators are best for treating large areas.These spreaders have vibrating opening plates that prevent clogging. Swathwidth is either pre-set or adjustable with a rheostat. Applicators canbe mounted on any vehicle that will maintain a low speed. Do not use ground-drivenor power take off-driven equipment, since it can rarely be set to applysuch a low rate. Aerial application requires some modifications to theaircraft and application equipment. A description of these relatively simplemodifications and calibration methods can be obtained from bait productmanufacturers.

In addition to their use as a broadcast treatment, baits can be usedfor individual mound treatment or spot treatment. Compared to other moundtreatment products, baits cause less hazard to the environment and lessmound relocation. Several bait products (hydramethylnon, sulfonamide) areavailable in stations to place where ants are foraging (indoors or outdoors).

Individual mound treatments. In addition to baits, mound treatmentinsecticides are formulated as dusts, liquids, granules and aerosols. Theireffectiveness depends on proper application. Contact insecticides mustcontact ants to work and should be applied during times of the year whenants are close to the mound surface. It is also important not to disturbthe mound during treatment.

Mound drenches: Although a few are ready-to-use, most fire antmound drenches are formulated as liquid concentrates that must be dilutedin the amount of water specified on the label. Avoid skin contact withthe concentrate. Mix the proper amount in a gallon container, such as asprinkling can, plainly marked "POISON." Do not use the container for anyother purpose. Properly store or discard containers after use. Pour thesolution on top of and around the undisturbed mound. Most mound drenchesrequire several days to eliminate the colony, although those containingpyrethrins are effective almost immediately.

Granular products: To treat a single mound with a granular product,measure the recommended amount in a measuring cup and sprinkle it on topof and around the mound. Do not disturb the mound. If the label specifiesto water in the insecticide, use a sprinkling can and water the mound gentlyto avoid disturbing the colony. Several days may pass before the entirecolony is eliminated.

Dusts:tariffe basse negli alberghi di Sarvar Some products, such as those containing acephate(Orthene^®),are specially labeled for dusting individual fire ant mounds. Distributethe recommended amount of the powder evenly over the mound. Treated coloniesare usually eliminated in several days.

Injectable products: Products containing pyrethrins, resmethrin,tetramethrin or chlorpyrifos are manufactured in special aerosol containersto which an injection rod is attached. The rod is inserted into the moundin a number of places, according to instructions on the product label,and the pesticide is injected for a specified time into each mound. Specialequipment is required to apply PT^® 270 Dursban^®(chlorpyrifos) and Earthfire^® (resmethrin).

Surface applications and barriers in and around structures. Productsused to treat ant trails and colonies located in wall voids are usuallydusts or sprays, although some are insecticide-latex paint mixtures. Unlessthe colony itself is treated, these products only reduce the number offoraging worker ants. Surface treatments are also used to create barriersto protect items or areas from foraging worker ants. For a more detaileddiscussion of these methods refer to L-1783, "Carpenter Ants," and L-2061,"House Infesting Ants," available from the Texas Agricultural ExtensionService.

Surface applications outdoors. Granular insecticides are appliedwith fertilizer spreaders. These materials must be thoroughly watered intothe soil after application. Liquid formulations are applied with a high-volumehydraulic, hose-end or boom sprayer. Contact insecticides are usually long-acting(2 to 3 months), suppress foraging ants quickly, and prevent small moundsfrom becoming established. Through repeated use, these treatments can eliminatecolonies.

Red imported fire ant colonies consist of the brood and several types(castes) of adults:

* winged males (distinguished from the females by their smaller headsand black bodies);

* red-brown winged females;

* one or more queens (wingless, mated females); and

* workers (see Fig. 2).

Worker ants are wingless, sterile females. They protect the queen bydefending the nest from intruders, by feeding the queen only food thatthe workers have eaten first, and by moving the queen from danger. Theyalso forage and care for the developing brood. The brood is made up ofcream-colored eggs, larvae and pupae of all the castes.

The winged forms, or reproductives, live in the mound until their matingflight, which usually occurs in the afternoon soon after a rainy period.Mating flights are most common in spring and fall. Males die soon aftermating, while the fertilized queen alights to find a suitable nesting site,sheds her wings, and begins digging a chamber in which to start a new colony.Sometimes, several queens can be found within a single nesting site.

A newly-mated queen lays about a dozen eggs. When they hatch 7 to 10days later, the larvae are fed by the queen. Later on, a queen fed by workerants can lay up to 800 eggs per day. Larvae develop 6 to 10 days and thenpupate. Adults emerge in 9 to 15 days. The average colony contains 100,000to 500,000 workers and up to several hundred winged forms and queens. Queenants can live 7 years or more, while worker ants generally live about 5weeks, although they can survive much longer.

There are two kinds of red imported fire ants--the single queen andmultiple queen forms. Workers in single queen colonies are territorial.Workers from multiple queen colonies move freely from one mound to another,which has resulted in a dramatic increase in the number of mounds per acre.Areas infested with single queen colonies contain 40 to 150 mounds peracre (rarely more than 7 million ants per acre). In areas with multiplequeen colonies, there may be 200 or more mounds and 40 million ants peracre.

The red imported fire ant builds mounds in almost any type of soil,but prefers open, sunny areas such as pastures, parks, lawns, meadows andcultivated fields. Mounds can reach 18 inches in height, depending on thetype of soil. Often mounds are located in rotting logs and around stumpsand trees. Colonies also can occur in or under buildings.

Colonies frequently migrate from one site to another. The queen needsonly half a dozen workers to start a new colony. They can develop a newmound several hundred feet away from their previous location almost overnight.Flooding causes colonies to leave their mounds and float until they canreach land to establish a new mound. Colonies also can migrate to indoorlocations.

Fire ants can be beneficial. They feed primarily on insects and arthropodpests, which can reduce the need for insecticides in commercial agriculture.In urban areas fire ants feed on flea larvae, chinch bugs, cockroach eggs,ticks and other pests.

Medical Problems

Fire ants are aggressive, will defensively attack anything that disturbsthem, and can sting repeatedly. Symptoms of a fire ant sting include burning,itching and a white pustule that forms in a day or two. Although the stingsare not usually life threatening, they are easily infected and may leavepermanent scars. Some people become sensitive to fire ant stings and shouldseek the advice of an allergist. If a sting leads to chest pains, nausea,severe sweating, loss of breath, serious swelling or slurred speech, theperson should be taken to an emergency medical facility immediately. Somepeople may lapse into a coma from even one sting. Relatively few deathsfrom fire ant stings have been documented, compared to deaths from beeand wasp stings.

Tips for avoiding medical emergencies and for treating ant stings:

* Teach children and visitors about fire ants and their hazard.

* Wear protective clothing during outdoor activities. Wear shoes orboots and/or tuck pant legs into socks.

* Treat stings with an insect bite remedy containing benzocaine or otheringredients that deaden pain and protect against infection.

* Control fire ants in areas used most
frequently by people and pets.

History and Control Efforts

More than 60 years ago, the red imported fire ant was accidentally broughtinto Mobile, Alabama from South America. It now infests more than 260 millionacres comprising most of nine southeastern states and Puerto Rico. It reachedTexas during the 1950s and spread steadily across the state. Fire antscan travel long distances when newly-mated queens land on cars, trucksor trains. Shipments of nursery stock or soil from an infested area mayrelocate entire colonies or nests. The fire ant presently infests the easterntwo-thirds of Texas and continues to spread westward (Fig. 1, p. 8).

Efforts at county-wide fire ant eradication during the late 1960s andearly 1970s, although they used effective pesticide baits, were not successful.The last large-scale aerial treatments were applied to Madison, Kerr andKendall counties in 1981 and 1983. Why did eradication programs fail? Thereasons are debatable, but it is now known that eradication is hinderedby the ant's biology and by problems with treatment methods.

Biological obstacles to eradication. The ants infest suchan extensive area that a single treatment would take years and massiveresources to apply. Fire ants have a high reproductive rate and disperseeasily. Thousands of reproductive females are produced per colony, andthe mated females begin a colony wherever they land. The ants eliminatecompeting insects and then rapidly overwhelm an area. Whole colonies canmove, and in the multiple queen form, the colonies can split into manynew colonies. The queen is protected from many poison baits, since sheis fed only food eaten first by workers. If a poison works too rapidly,the worker is killed before the poison is passed to the queen. Finally,worker ants from well-fed colonies may not forage on a bait product, ora bait may not be as attractive as some abundant natural food.

Pesticidal obstacles to eradication. Pesticide treatmentsare expensive and time-consuming, and there are only three basic approaches.The first is surface treatment using a residual contact poison.This approach is the least environmentally sound because the treated surfaceremains toxic for a long time. The ants may survive by foraging underground.The second is individual mound treatment, which involves the applicationof a large volume of pesticide to reach the queen. However, it is hardto manipulate large volumes of liquid, and treatment is more expensiveand time-consuming. Colonies not eliminated may move or split into severalcolonies. The third method is bait treatment, which uses some sortof attractive substance the ants like to eat. Unfortunately, baits arenot always consumed, and the bait's attractiveness is short-lived. Thepesticide must be slow-acting and effective over a range of doses, sincethe dose the ants get cannot be controlled. Baits may also kill ant speciesthat compete with the fire ant and help control it.

Economic, regulatory and environmental obstacles to eradication.The best way to treat large areas (hundreds of acres) is aerial applicationof bait. However, not all areas can be treated because of label restrictionsand application limitations. Even with a bait product, it is not feasibleto treat the entire infested area or even a large part of a single state,and untreated areas are sources for reinfestation. The larger the treatmentarea the more slowly reinfestation occurs. If periodic treatments are discontinued,the area may become just as infested as it originally was within a yearor two.

Table 1. Fire ant insecticides, modes of action andformulations, with generic names of active ingredients and some examplesof product names.

Insect Growth Regulator (fenoxycarb) ­ This material mimicsthe effects of the insect's own juvenile hormone, reducing the productionof viable eggs and preventing the development of worker ants for up toa year after application. It does not kill adult insects. Treated ant coloniespersist for several months after treatment, until worker ants present atthe time of treatment die naturally. Fenoxycarb is formulated as a baitto be applied to individual mounds or broadcast. (Award, Logic®)

Botanicals (pyrethrins, rotenone, pine oil, turpentine) ­These plant-derived products are contact insecticides andhave various modes of action. Pyrethrins, which act on the nerve axon,kill ants quickly (within minutes to hours) and can be used as mound treatmentsor surface sprays. Rotenone acts on the respiratory tissues, includingnerves and muscles. Pyrethrins and rotenone products break down rapidlyin the environment. Rotenone and pine oil (turpentine) products are relativelyslow-acting (days to weeks) and are applied as mound drenches.(Insecto^®Formula 7, Organic Plus^® Fire Ant Killer, and others)

Derivatives of Pyrethrins (allethrin, resmethrin, sumithrin,tetramethrin) ­ Like pyrethrins, these products destabilize nerve cellmembranes and kill quickly, but are quickly deactivated and have littleresidual activity. They are contact insecticides appliedas aerosol injections, mound drenches or surface sprays. (Enforcer^®Fire Ant Killer)

Pyrethroids (bifenthrin, cyfluthrin, cypermethrin, fenvalerate,fluvalinate, lambda-cyhalothrin, permethrin, s-bioallethrin, s-fenvalerate,tefluthrin, tralomethrin) ­ These products also destabilize nerve cellmembranes. They can persist in the environment longer than pyrethrins andtheir derivatives. They are relatively quick-killing contact insecticidesapplied as mound drenches, dusts or surface sprays and granules.

Avermectins (abamectin) ­ This bait productis derived from a soil fungus and inhibits nerve transmission. As a moundtreatment it kills worker ants and colonies quickly, but as a broadcasttreatment it acts more like an insect growth regulator, preventing theproduction of viable eggs. (Ascend)

Carbamates (bendiocarb, carbaryl) ­ These materials disruptnerve transmission (cholinesterase inhibitor). They are relatively quick-killingcontact insecticides used as mound drenches and surface sprays.(Sevin^®, Turcam^®)

Organophosphates (acephate, chlorpyrifos, diazinon, dichlorvos,fenthion, isofenphos, malathion, propetamphos, propoxur, trichlorfon) ­These products also interfere with nerve cell transmission (cholinesteraseinhibitor). They are relatively quick-killing contact insecticidesformulated as aerosols, liquids, dusts or granules and applied as moundtreatments or surface applications. (Dursban^®,Oftanol^®,Orthene^® and others)

Miscellaneous Compounds ­ Hydramethylnon (amidinohydrazone)and sulfonamide kill ants by preventing them from converting food intoenergy. These baits eliminate fire ant colonies within aweek when applied to individual mounds, but take several weeks when broadcast.They are also formulated in bait stations. (Amdro^®,Combat^®,MaxForce^®, Raid^® Max)

Inorganic Compounds ­ Boric acid is a slow-acting stomachpoison. It is commonly formulated as a dust or liquid baitfor control of ants. Diatomaceous earth (D.E., silicone dioxide) productsare usually applied as contact insecticides to ant trailsindoors. D.E. abrades the waxy layer from the insect exoskeleton, causingthe insect to desiccate. However, D.E. does not eliminate colonies withintreated mounds. When D.E. is used as a carrier in formulations of pyrethrins,it may enhance penetration of this botanical insecticide into insect bodies.
 
The user is always responsible for the effects of pesticide residues,as well as for problems that could arise from drift or movement of thepesticide to neighboring areas. ALWAYS READ AND FOLLOW CAREFULLY THEINSTRUCTIONSON THE CONTAINER LABEL. Pesticides must be registered and labeled for useby the U. S. Environmental Protection Agency and the Texas Department ofAgriculture. The status of pesticide label clearances is subject to changeand may have changed since this publication was printed.

The authors are grateful for reviews of earlier drafts of this publicationby Dr. David Oi, Les Greenberg and Sherry Ellison.

Educational programs of the Texas Agricultural Extension Serviceare open to all people without regard to race, color, sex, disability,religion, age or national origin.
 
 

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