When it comes to insect pests, fire ants would probably top everyone’s list! Red and black imported fire ants (Solenopsis invicta and Solenopsis richteri) are invasive species and their painful bites can injure or kill livestock, wildlife, domestic animals, and humans. Their large mounds (as many as 300 per acre) are unsightly and often damage mowers and other equipment. Fire ants also infest buildings and can damage electrical equipment by chewing on wire insulation.
In the United States, fireants cost $6 billion a year, including the cost of insecticides The Two-Step Method and other approaches described here can lower that cost while reducing environmental damage and improving fire ant control. Knowing your options will allow you to make better choices to protect your family, pets, and property.
Identifying Fire Ants
There are hundreds of ant species in the southern United States, including some native fire ant species, and most of them are con- sidered beneficial insects. Collectively, ants till more earth than earthworms, and some prey on other insect pests to help reduce pest numbers.
Fire ants usually build mounds and will build them almost anywhere—in the open or next to a building, tree, sidewalk, or electrical box. When the mound is disturbed, fire ants can emerge quickly from any opening created by the disturbance or from sev- eral natural holes, and begin biting and stinging. They will readily run up vertical surfaces.
Worker fire ants are dark reddish-brown with shiny black abdomens, and vary in size from about 1/16- to about 1/4-inch long. Fire ants are similar in appearance to many other ants,
so make sure you have correctly identified the species before attempting to solve your ant problem (
Controlling Fire Ants
Most people (about 80 percent according to one survey) try to control fire ants by treating individual ant mounds. Mound treat- ments are expensive, up to $2 or more per mound, and require lots of time and labor if you have much land to treat. You can easily use too much insecticide, which may lead to environmental contami- nation if rain washes the insecticide into lakes and streams. To be effective, the mound treatment must kill the queen(s). Otherwise, the colony will survive. Some nests may go undetected. Even an area where every mound has been treated can soon be reinfested by fire ant colonies migrating from untreated areas or floating there on floodwater. Also, deep-dwelling colonies that escaped mound treatment can quickly form mounds after a soaking rain. It is usu- ally more effective and less expensive for homeowners to treat the entire yard with a bait product designed for broadcast application.
Fire ants cannot be eliminated entirely because it is not possible to treat all infested areas. There may not be a single
best method for fire ant control, especially in large areas. Your objective should be to find the method or methods that are most cost-effective, environmentally sound, and fit your tolerance level for fire ants. In areas where these ants do not present problems, doing nothing is one option. Another option is to implement an integrated pest management (IPM) program. IPM incorporates cultural (nonchemical), biological control methods and the selec- tive use of insecticides.
◆ Biological control:
Government and university researchers have imported and tested natural enemies of fire ants, such as parasitic decapitating flies from South America. These natural enemies have successfully established in areas where they have been released. They are not available to the general public; however, ongoing release programs in all infested states are making decapitating flies more prevalent in the environment. These flies are extremely host-specific to the imported fire ants, making it impossible for them to negatively impact other ant species. Biological control agents available on the retail market such as parasitic nematodes do not sustain themselves or spread on their own once they are released.
- ◆ Home remedies: Many home remedies have been devised
to control fire ants. Drenching a mound with 2 to 3 gallons of almost boiling water eliminates ant colonies about 60 percent of the time, but it will also kill plants the water contacts. This method is labor-intensive and the hot water must be handled carefully. Some home remedies, such as applying instant grits, molasses, aspartame, or club soda to ant mounds do not work. Pouring chlorine, ammonia, gasoline, or diesel fuel on mounds frequently causes fire ant colonies to relocate but can contaminate the soil and groundwater, is dangerous, and strongly discouraged.
- ◆ Organic products: A few products are certified as organic). These include ingredients such as d-limonene, an extract from citrus oil, and spinosad, a chemical complex produced by a soil microbe and formulated as a bait or liquid ant mound drench treatment.
◆ Chemical control:
The use of insecticides for fire ant control is regulated by the Environmental Protection Agency. Approved products must be used according to label directions. Read the label carefully! An approved product is one that has directions for fire ant control on the label. Be sure the label lists directions for where you intend to use it, particularly if you will be treating a vegetable garden or other food produc- tion site). Products for use in electrical utility boxes and indoors may be available only at specialty stores. Some products are for use only by professional pest control operators.
Most active ingredients are marketed under more than one brand or trade name. Product names and the ingredients they con- tain change over time. This publication refers to the generic names of the active ingredient contents in insecticides, which you should see on the product labels. Some sample trade names are given as well.
Products are formulated as dusts, granules, liquid drenches, or baits. They are applied either to individual ant mounds or across the surface of the ground (broadcast). The various active ingredients affect ants in different ways.
Baits contain active ingredients dissolved in a substance ants eat or drink. Some bait ingredients affect the nervous system. To be effective, baits must be fresh and applied when ants are actively foraging. To determine if the time is right for treatment, place a small amount of bait in the area to be treated and see if foraging ants remove it within an hour. Because ants collect bait and return it to the colony, very little insecticide is needed. Baits are ruined by water, so do not water baits after application or apply them when rain is expected.
The Two-Step Method.
◆ Step 1. Broadcast a fire ant bait once or twice a year to reduce fire ant colonies by 80 to 90 percent.
◆ Step 2. Treat nuisance ant mounds such as colonies that move into the bait-treated areas. Step 2 may not be needed.
Treat nuisance ant mounds or colonies with a contact insecticide applied as an individual mound treatment. To allow ants to consume the bait, treat nuisance mounds no sooner than 24 hours after bait application.
Contact Insecticide Treatments
With this approach, a contact insecticide is applied to the lawn and landscape surface. This is more expensive than other control methods but it may be more effective in smaller areas because ants that move into treated areas will be eliminated as long as the chem-
Always read and follow the application instructions on the label of the product you are using. Use a handheld spreader/seeder for baits that are applied at very low rates such as 1 to 5 pounds of product per acre. Use the push-type spreader for baits that are applied at higher volumes per acre (2 to 5 pounds per 5000 square feet). Granular products are best applied with a push-type fertilizer spreader and must be watered in after treatment. Granular fipronil products, such as restricted-use professional products Top Choice or Taurus, are slower acting but longer lasting; only one treatment is permitted per year. Faster-acting contact insecticides, such as the pyrethroids (listed above), eliminate ants on the surface for months but may not eliminate colonies nesting deeper in the soil.
Make a Management Plan
Chemical control lasts only as long as the effects of the insecticide used, until new ant colonies move in from untreated areas, or mated queens arrive to start new colonies. You can expect an ant infestation to return to its original level eventually. Thus, keeping fire ants in check requires a commitment of time and money.
To reduce the cost and make control easier, consider making a map of your property. Divide larger landscapes into treatment areas and designate the most appropriate treatment approach for each area. Make and maintain a schedule for the first treatment and any necessary re-treatments.
For example, you might use a long-residual broadcast contact insecticide at regular intervals in high-value or high-traffic areas (near buildings or in play or recreation areas) where maximum control is needed. In other areas, where 80 to 90 percent control of ants is acceptable, you might use the Two-Step Method. Because control lasts longer when large areas are treated, consider participating in a community- or neighborhood-wide treatment program. These have been shown to improve control and reduce cost. If everyone participates by making coordinated treatments, ant colonies will not be able to migrate from property to property and reapplications eliminate newly developing colonies.