En Fuego

Editor’s Note: This article is an excerpt from the new edition of the “PCT Field Guide for the Management of Structure-Infesting Ants,” recently published by Lawn & Landscape’s sister publication. Order it at www.lawnandlandscape.com/store.

Photo: advantage Green Lawn & Shrub CareThe three basic approaches for controlling fire ants are one or all of the following: (1) mound-to-mound treatment; (2) broadcast bait treatment or broadcast granular treatment; and (3) perimeter treatment.

Protecting some properties may involve a combination of these three methods. Large properties, however, may be feasibly treated primarily by broadcast baiting due to the expense of applying mound-to-mound techniques. Any mounds next to buildings on large properties can be treated by a mound-to-mound treatment technique followed by a perimeter treatment and/or baiting around the building.

Researchers at Texas A&M University recommend a two-step process for controlling fire ants. First, a broadcast fire ant bait is applied and allowed to sit for about two days thus permitting foraging workers to feed upon the bait, carry it into the nest and distribute it through the colony. Mound-to-mound treatments with conventional residual treatments as described below are then used to eliminate visible mounds.

Mound-to-Mound Treatment
Several methods may be used for treating individual fire ant mounds that will kill the mound within a few hours to a few weeks, depending on the product used.

A major disadvantage with using water-based residual drenches or mound injection is their labor-intensiveness because each mound must be located and individually treated. Additionally, such applications may result in “satelliting,” where surviving ants relocate to nearby sites and establish one or more new colonies. Smaller mounds are often overlooked and serve as reinfestation sources. Ants from adjacent properties often quickly reinvade treated properties.

Mound drench. The mound is flooded with a large volume of an appropriately labeled, water-based insecticide. More than one gallon is needed for most mounds and larger mounds may require several gallons. Drenches are most efficiently applied with a low-pressure power treating unit mounted on a truck. A disadvantage of this technique may be the failure to reach all areas of the mound to kill the queen or queens inside. Using too little volume may permit the survival of one or more queens and results in satelliting.

Mound injection. A few aerosol and water-based insecticides are labeled for direct injection into fire ant mounds. This technique is typically more effective at penetrating throughout the mound than mound drenching.

Baits. Baits labeled for fire ants may be used for individual mound treatment. A small amount of bait, usually a tablespoon or less, is applied onto and up to 3 feet around a mound. The great disadvantage of using baits to treat mounds is the length of time it may take for results to occur. New fire ant baits, however, can kill mounds within as quickly as 24 hours and are less labor intensive than mound drenching.

Powders or dusts. A few dry, dust or powder products may be labeled for direct application to fire ant mounds.

Broadcast Bait Treatment
Fire ant baits may be applied to large areas (e.g., lawns) using various types of spreading equipment. Baits are found by foraging fire ants and carried into the mound to be fed to other workers, larvae and the queen(s).

The advantages of broadcast baits is their ease of application to large areas, control of unseen and small mounds and control of some of the colonies located on neighboring properties. Complete control is often not achieved, however, due to: (1) ants from some mounds avoid the bait; (2) the bait fails to drop close enough to some colonies to be discovered by foragers; (3) the baits are sensitive to sunlight and moisture and break down quickly; and (4) the baits are not specific to the fire ant and competing ant species may remove the bait.

Broadcast bait treatments are most effective when combined with mound-to-mound treatments.

The amount of bait actually applied is quite small (1 to 1½ pounds per acre or less than ½ ounce per 1,000 ft2) and requires a spreader capable of low-volume application of dry materials.

A University of Florida publication, “Imported Fire Ants and Their Management in Florida,” recommends the following when using baits for fire ants: (1) “use fresh bait;” (2) “apply baits when the grass and ground are dry or drying and rain is not expected, preferably for the next 24 hours;” and (3) “apply baits in late afternoon or evening” because fire ants will forage at night during the summer.

Perimeter Treatment
The application of a water-based residual product to the foundation and landscaping around a building where fire ants are present on the property can be beneficial in limiting indoor foraging by fire ants.

Perimeter treatments may be applied whenever ants are found near or next to the building. Mounds living in landscape mulch may need to be exposed by raking back the mulch and drenching each mound thoroughly.

The author is technical director of Terminix International, Memphis, Tenn. Contact him via e-mail at shedges@giemedia.com.