Imported Fire Ants in Tennessee

Chemical Control

Pesticides are products designed to kill target organisms. An insecticide is a pesticide formulated to kill insects. Using chemical insecticides (both “organic” and synthetic) continue to be the main method of battling fire ants. Insecticides registered by the EPA are considered to pose minimal risk to the user and the environment when used as directed. Insecticide applications can be aimed at the foraging ants and/or at the entire colony. Table 1 lists fire ant insecticides by generic names of active ingredients.Carefully follow directions on the product label for the proper method of application, the use of protective clothing, re-entry intervals and watering practices before and after treatment.

Baits

Most conventional bait formulations combine pesticide ingredients with soybean oil, which is absorbed onto processed corn grit. Soybean oil is an attractive food for ants that is important to the success of the bait. Because these baits are granular in texture, be careful not to confuse them with granular products that contain contact insecticides (see Table 1). Fire ant baits should have the word “BAIT” clearly listed on the label. Baits can be applied as spot treatments to individual mounds or broadcast over larger areas. To achieve satisfactory results:

1	Use fresh bait, preferably from a just opened container or one which has been tightly resealed and stored for no more than 2 years. Purchase only enough bait to make one treatment and do not store large quantities once the containers have been opened. Bait is collected by ants only when it is fresh. It is then carried back to the colony and shared with other members of the colony. Rancid or stale bait is ignored by foraging ants. To check the quality of your bait, place a little near an ant mound to see if ants are attracted to it, as described below. Rancid bait also often has a pungent, “latex paint” odor.
2	Apply when worker ants are actively foraging. This can also be determined by leaving a small pile, e.g., 1 to 2 tablespoons, of bait in the area to be treated. When ants are seen actively removing the bait 10 to 30 minutes later, you will know that the bait is attractive to ants and that ants are foraging. You can also use tuna fish, pet food or potato chips to see if ants are foraging. Foraging activity slows when soil temperature is lower than 65 to 70 degrees F or higher than 90 degrees F. In mid-summer, apply bait in late afternoon or early evening, because foraging ants are less active during the heat of the day.
3	Apply baits when the ground and grass are dry and no rain is expected.
4	Do not mix bait with other materials such as fertilizer or seed.
5	Use appropriate application equipment and calibrate it properly. Differences in the oiliness of bait brands and production batches can cause variations in applicator output. Temperature and humidity also affect the rate at which bait flows through the applicator opening. The speed at which the applicator is moving is an important factor, particularly with factory-calibrated settings. Over-application provides little or no increase in control and adds greatly to the cost. Under-application may decrease effectiveness.

The availability of bait products is a problem, especially in areas recently invaded by the fire ant. If you cannot find some of the products mentioned in this publication, contact the store manager, visit your local co-op or contact your county Extension agent to determine if the product is available in your area. Sometimes many of the bait products are sold only through specialty stores such as lawn and garden supply stores or pesticide wholesalers that sell professional products.

Bait application usind a hand spreader Hand-operated spreaders such as the EarthWay® Ev-N-Spred and Scott’s® HandyGreen® are ideal for treating small areas with fire ant baits. The operator can walk or ride on the back of a vehicle. Some push-type applicators, such as Spyker® Models 24 and 44, also may be suitable, but some modification (attach fire ant plate) is required to keep from applying too much material. Most rotary and drop-type fertilizer spreaders will not apply fire ant baits at the recommended rate.

Electric spreaders such as the Herd® Model GT-77A or similar applicators are best for treating large areas. These spreaders have vibrating opening plates that prevent clogging. Swath width is either pre-set or adjustable with a rheostat. Applicators can be mounted on any vehicle that will maintain a low speed. Do not use ground-driven or power take off-driven equipment, because it can rarely be set to apply such a low rate. Aerial application requires some modifications to the aircraft and application equipment. A description of these relatively simple modifications and calibration methods can be obtained from bait product manufacturers.

In addition to their use as a broadcast treatment, baits can be used for an individual mound treatment or spot treatment. Compared to other mound treatment products, baits cause less hazard to the environment and less mound relocation. Several bait products (hydramethylnon, sulfluramid) are available in bait stations that you place where ants are foraging (indoors or outdoors). Bait products containing indoxacarb, hydramethylnon, abamectin or spinosad used to treat individual ant colonies work faster than when broadcast-applied. This is, however, not the case with insect growth regulator (IGR) baits containing fenoxycarb, methoprene or pyriproxyfen. Apply bait products as directed on the product label.

Individual mound treatments with contact insecticides

In addition to baits, mound treatment insecticides are formulated as dusts, liquids, granules and aerosols. Their effectiveness depends on proper application. Contact insecticides must contact ants to work and should be applied during times of the year (and times of the day) when ants are close to the mound surface. It is also important not to disturb the mound during treatment if this is stated on the product label. Individual mound treatment selectively eliminates only the ant colonies treated, and preserves desirable competitor ant species.

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Do not apply more products than specified on the label. Water it properly.

Application of bait to individual ant mound

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Application of dust to individual ant mounds

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Mound drenches

Although a few are ready-to-use, most fire ant mound drenches are formulated as liquid concentrates that must be diluted in the amount of water specified on the label. Avoid skin contact with the concentrate or mixture. Mix the proper amount in a gallon container, such as a sprinkling can, plainly marked “POISON.” Do not use the container for any other purpose. Properly store or discard containers after use. Pour the solution on top of and around an undisturbed mound. Most mound drenches require a day or two to eliminate the colony, although those containing pyrethrins 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 top of and around the mound. Do not disturb the mound. If the label specifies to water in the insecticide, use a sprinkling can and water the mound gently to avoid disturbing the colony. Several days may pass before the entire colony is eliminated.

Dusts

Some products, such as those containing acephate (Orthene®), are specially labeled for dusting individual fire ant mounds. Distribute the recommended amount of the powder evenly over the mound. Treatments work best when ants are near the top of the undisturbed mound. Treated colonies are usually eliminated in several days.

Injectable products

Products containing pyrethrins, resmethrin, tetramethrin or chlorpyrifos are manufactured in special aerosol containers to which an injection rod is attached. The rod is inserted into the mound in a number of places, according to instructions on the product label, and the pesticide is injected for a specified time into each mound.

Surface applications and barriers in and around structures

Products used to treat ant trails and colonies in wall voids are usually dusts or sprays, although some are mixtures of insecticide and latex paint. Unless the colony itself is treated, these products only reduce the number of foraging worker ants. Surface treatments are also used to create barriers to protect items or areas from foraging worker ants.

Surface applications outdoors

Granular insecticides are applied with fertilizer spreaders. These materials must be thoroughly watered into the soil after application. Liquid formulations are applied with a high-volume hydraulic, hose-end or boom sprayer. Some contact insecticides are relatively long-acting (weeks to months), suppress foraging ants quickly, and prevent small mounds from becoming established. Through repeated use, these treatments can eliminate colonies.

Organic Insecticides

Any chemical product sold with a claim that it kills fire ants must be registered by the Environmental Protection Agency (EPA) or approved by the appropriate state regulatory agency. Several products said to be “organic” (of natural origin) are currently marketed for fire ant control. All of these products are registered by the EPA as pesticides and some are very effective. However, they are not necessarily safer than other insecticides, and should be used with care.

For more information on using organic insecticides see "Organic Two-Step Method for Imported Fire Ant Control".


Experiment Station, Extension Service, College of Vet Medicine, College of Agriculture, Institute of Agriculture


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