Management Options of Fire Ants for Home Lawns and Ornamental Turf

Imported Fire Ants February 20, 2015 Print Friendly and PDF

Home Lawns and Other Ornamental Turf

Fire ants commonly infest lawns, schoolyards, athletic fields, golf courses and parks, where they pose a medical threat to people and animals. Their mounds also detract from the appearance of the landscape and can damage lawn care equipment.

Program 1. The “Two-Step Method”:

This program suppresses ants in ornamental turf and non-agricultural lands, including roadsides. It is also suitable for pasture and rangeland if the products selected are specifically registered for use in these sites. Similarly, an "organic two-step" program can be implemented using a bait and a mound treatment combination considered "organic" or using products certified by the Organic Materials Review Institute (OMRI). This approach is best suited to medium-sized or large areas, and the cost is moderate. It is not suggested for use in previously untreated areas with few fire ant mounds (20 per acre or fewer, or 0.46 or fewer per 1,000 square feet). Some bait products may affect native ants that compete with imported fire ants. The goal of this program is to reduce fire ant problems while minimizing the need to treat individual mounds.

The two steps involve: 1) broadcasting a bait product (see the section on Baits in Fire Ant Treatment Methods), followed by 2) treating nuisance mounds with a faster acting individual mound treatment or with a mound re-treatment of the bait.

  • Step 1. Once or twice per year, usually in spring and fall, broadcast a bait-formulated insecticide or use an outdoor bait station product as directed on the label. Most conventional baits are applied at a rate of 1 to 1 1⁄2 pounds of product per acre, although some products are applied at higher rates. Periodic broadcast applications of fire ant baits will provide about 90 percent control when properly applied. A bait can be broadcast with hand-held, vehicle-mounted or aerial applicators. The speed and duration of ant suppression differs with the product used. Hydramethylnon, fipronil, indoxacarb, metaflumazone and spinosad baits (see the section on Fire Ant Insecticides) provide maximum control 1 to 4 weeks after application, while insect growth regulator (IGR) bait products (i.e., those containing fenoxycarb, methoprene or pyriproxyfen) provide maximum suppression 2 to 6 months after treatment depending on environmental conditions. Abamectin baits act more slowly than hydramethylnon, fipronil, indoxacarb, metaflumazone and spinosad but more quickly than IGR products. A late summer IGR application provides maximum suppression the following spring. Using higher rates of an IGR bait does not eliminate colonies more quickly. The blending of half rates of a faster acting bait plus a n IGR (such as hydramethylnon plus methoprene as in the product Extinguish® Plus and Amdro Fire Strike Fire Ant Bait for Broadcast Yard Treatment, or as directed on AmdroPro® and Extinguish® product labels) can provide faster and longer lasting suppression. Where there are many mounds per acre (200 or more), a second application may be needed after the maximum effects of the first treatment have occurred, because not all mounds are affected by a single bait application. Follow label instructions on any time interval requirements between applications and limits on number of applications per year.
  • Step 2. Preferably, wait several days or more after broadcasting the bait, and then treat nuisance ant colonies (such as those in sensitive or high-traffic areas) using an individual mound treatment method (see Program 2, Step 1, below). Otherwise, be patient and wait for the bait treatment to work. Any nuisance mounds that escaped the effects of bait treatment, and any colonies migrating into treated areas, should be treated as needed. In large areas, individual mound treatment may not be feasible and routine broadcast bait treatments alone may provide sufficient control.

Repeat the bait application when ants re-invade the area and mound numbers reach about 20 per acre or exceed the tolerance level for a situation. Bait products do not protect against reinvasion by ant colonies from surrounding land or by newly mated queens. Ant populations can fully recover within 12 to 18 months of the last bait treatment. Low-lying, moist and flood-prone areas are more prone to re-infestation.

Program 2. Individual Mound Treatments:

This approach is 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 preservation of native ants is desired. This program selectively controls fire ants, but rapid re-invasion should be anticipated. It generally requires more labor and monitoring than other programs, and is not suggested for large or heavily infested areas.

Individual fire ant mound treatment (photo by B. Drees).
  • Step 1. Treat undesirable fire ant mounds using an individual mound treatment (see the section on Individual Mound Treatments with Contact Insecticides under Fire Ant Treatment Methods). Products are applied as dusts, dry granules, granules drenched with water after application, liquid drenches or baits. Non-chemical treatment methods such as drenching mounds with very hot water also may be used. Mound treatments may need to be repeated to eliminate the colony if queen ants are not all killed with the initial treatment. When treating an ant mound with a liquid product or watering a product into a mound, begin on the outside of the mound and circle into the center of the mound. Application of faster-acting granular ant bait formulations are made around the mound as directed.
  • Step 2. Continue treating undesirable mounds that appear, as needed.

Program 3. The Long-Residual Contact Insecticide Treatment Method:

This program eliminates many ant species in treated areas and it reduces re-invasion of treated areas as long as the contact insecticide remains effective. However, these products are more expensive, use more insecticide, and have greater environmental impact than other methods. This approach is frequently used by commercial applicators for treating ornamental turf. Long-residual products that contain a pyrethroid usually work most rapidly. Fipronil granular products eliminate ant colonies more slowly but have longer residual effects.

  • Step 1. (Optional). Broadcast a bait-formulated insecticide in areas where there are many mounds (more than 20 per acre), or individually treat fire ant mounds. Wait 2 to 3 days after applying a bait before conducting the next step.
  • Step 2. Apply a contact insecticide with long residual activity (i.e., fipronil or a pyrethroid such as bifenthrin, deltamethrin,gamma-cyhalothrin or lambda-cyhalothrin) to turfgrass as directed (generally every 4 to 8 weeks for most products, or once per year using a granular fipronil product). Liquid or granular products (which are usually watered in after application) that can be evenly applied to an area are appropriate for this use. With most products, the initial surface treatment may not eliminate ants located deep in mounds, but routine re-application will eventually eliminate most colonies. Fipronil, a non-repellent contact insecticide that can be used with bait products, will eliminate ant colonies within 4 to 10 weeks of treatment, even those nesting well beneath the surface. However, ants migrating into treated areas may take more than a week to be eliminated.

Program combinations:

Any of the three programs can be mixed and matched within a managed area where different levels of fire ant control are desired. On golf courses, for instance, Program 3 might be suitable for high-use areas such as putting greens and tee boxes. In fairways and rough areas, Program 1 might be sufficient. On athletic fields, where as many ants as possible must be eliminated, Program 3 should be used, and the program should begin early enough to attain maximum suppression by the time the field is in full use. People with severe allergies to fire ant stings should follow Program 3 for their lawns or use a bait on a calendar schedule. For grounds around schools, day care centers, mental health facilities, and other sensitive sites, broadcast application of a fire ant bait product twice per year is one of the least-toxic methods of control. Control should be monitored with routine surveillance for re-invading ant mounds that need to be treated.

In some states, special regulations may govern the selection and use of fire ant products on school grounds. In Texas, for example, all pesticide applications must be made by licensed applicators. Schools in Texas are encouraged to use botanical, microbial, or insect growth regulator insecticides because of their extra high margin of safety. Appropriate bait treatments for Texas schools include formulations containing abamectin, spinosad, pyriproxifen or methoprene. Good first choices for mound treatments around schools and other sensitive areas include botanical insecticides containing pyrethrins, d-limonene or other natural compounds such as spinosad. For the greatest degree of safety, use only formulations that are washed immediately into the mound and leave minimal surface residue. Laws governing pesticide use in and around schools are subject to change each year. If in doubt about laws governing pesticide use around schools in your state, contact your state’s lead agency for pesticide regulation. State-by-state summaries of pesticide laws can be found on the Internet at NPMA Pestworld.

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.