Sustainable Fire Ant Management
The red imported fire ant is a well-known and troublesome pest throughout the southeastern United States. This invasive species is aggressive,and their painful stings can injure both humans and animals. The nuisances and hazards of fire ants cause many people to seek a “quick-fix” control strategy.
The high demand for a fast solution has led to the development of many “home remedies” and practices advertised as alternatives to pesticide treatments. Most of these have not been scientifically tested, and many have proven ineffective. But, some control efforts do hold promise for sustainable solutions to manage fire ants.
Fire Ant Ecology Basics
Red imported fire ants prefer open, sunny areas such as pastures, crop fields, and lawns. They will form either single-queen or multi-queen colonies. Multi-queen colonies are not territorial.
Fire ant nests usually take the form of large dirt mounds, but ants will also nest in rotting logs; around trees; under pavement and buildings; indoors; or inside electrical equipment and utilities, which sometimes causes short circuits. Fire ant nests will not have a single nest entry, but rather, several entrances under the mound. When the nest is disturbed, many fire ants will swarm out to attack the intruder.
Fire ants are omnivorous. They eat plants, insects, oils, and sugars, but they are only able to ingest liquids. Larvae break down solid food into liquids for fire ants by regurgitating digestive enzymes onto the food.
Sustainable Control Methods
To eliminate a colony, the queen must be killed; in multi-queen colonies, all queens must be killed. Even if the queen is killed, surviving ants may inhabit the mound or make a new mound until they die off.
Baits can be used as a broadcast or individual mound treatment. Conventional recommended treatments involve a “two step” process of broadcast bait treatments and individual mound treatments. But, broadcast baiting may be counterproductive because it can also decrease native ant populations that slow fire ant spread. If there are native ants in your treatment area, try using only individual mound treatments to prevent affecting non-target ant populations.
Least Toxic Pesticides
Hydramethylnon and sulfluramid kill ants by preventing them from converting food into energy.
Avermectin is derived from a soil fungus and inhibits nerve function. As a broadcast treatment it works like an insect growth regulator.
Insect growth regulators that reduce egg production and prevent worker ant development include fenoxycarb, methoprene, and pyriproxyfen. These treatments do not kill adult ants, so treated colonies will persist until workers die naturally.
Commercially available organic products that contain ingredients such as boric acid or diatomaceous earth can kill ants, but their effectiveness to kill whole colonies has not been consistently demonstrated.
Some products available have ingredients that are derived from botanical sources, such as rotenone, nicotine sulfate, d-limonene, and pyrethrins.
Spinosad is another toxin that affects the nervous system. Spinosad is considered organic because it comes from a bacterial fermentation process and is then put into bait.
Look for products certified by OMRI (Organic Materials Review Institute).
Treatments may be more effective on sunny, cool mornings when the majority of ants and brood are closer to the surface of the mound.
Scalding water (190ºF-212ºF) has been used on mounds with an elimination success rate of 20%-60%. Slowly pour at least 3 gallons onto the mound, being careful to avoid getting burned. A mound may need several treatments to reach and kill the queen and brood. Hot water may injure plants near the mound.
Fire ant mounds can be dug up and removed. Apply baby powder or talcum to shovel handles and the inside of the bucket to keep ants from crawling up and escaping or stinging you.
A Texas A&M Extension study showed potential success with a mound drench treatment of 1.5 fluid ounce of orange oil and 3 fluid ounces of liquid dish soap per gallon of water. After one week, there was a significant reduction in the number of active mounds in the treatment plots compared to other treatments. Researchers did cite the need for future studies to confirm the effectiveness of this treatment.
Sample Low Pesticide Treatment Option
- (Optional) Broadcast a bait-formulated insecticide.
- At least 3 days after baiting (if applied), drench individual mounds with hot water.
- Excavate and/or reapply hot water to mounds that are still active. Repeat as necessary.
- (Optional) Semi- or annually broadcast a bait-formulated insecticide to suppress reinfestations.
Many home remedies and control devices have not been scientifically proven to reduce fire ant populations. Most of the time these treatments just disturb the mound or kill enough ants to cause the colony to relocate. If the queens are not killed, the colony will not be destroyed and will most likely establish itself in another nearby area.
The following are some popular “home remedies” that do not control fire ant populations:
- Club Soda. One myth is that pouring club soda onto mounds suffocates the colony. This method is ineffective and at most may only drown a few ants. This method has been promoted on the Internet along with an inaccurate statement that the method is recommended by Walter Reeves of the University of Georgia.
- Grits. Fire ants only ingest liquids, so the idea that they will eat the grits, swell, and then explode is false.
- Soap or wood ashes. These substances supposedly remove the wax layer that protects the ant’s body, which is not true.
- Shoveling mounds together. Multi-queen colonies are not territorial and this method is not even effective for single-queen colonies. Florida has multi-queen populations, so by following this ineffective method you risk increasing your fire ant problem.
Some “non-pesticide” treatments are harmful to the environment and dangerous to apply. These include gasoline or petroleum products, battery acid, bleach, ammonia, or other cleaning products.
One reason fire ants are such resilient and successful invaders is that they have little competition and no natural enemies in the United States. To try to counter this imbalance, scientists began releasing phorid flies from fire ants’ native South America in the 1990s. Phorid flies are a natural parasite of fire ants in their home range. These flies lay their eggs in the ants’ heads; as the larvae develop, they take over (“zombify”) and eventually decapitate their ant host.
The USDA is releasing a fifth species of phorid fly to control fire ants in the southeastern US. Pseudacteon cultellatus is being released at several sites in Florida to help control workers in multi-queen colonies. Of the four species released previously, three have become widely established and expanded beyond their release sites.
UF/IFAS scientists have been researching biological control methods for fire ants and recently published a study that shows that there is potential to use a type of fungi as a control method against these creatures.
Unfortunately, no control method will permanently eliminate fire ants from an area. Fire ants can quickly re-infest areas after treatment stops, and may even resurge with greater populations. Because successful fire ant management techniques and products differ across localities, be sure to speak with your county’s Extension agent for management tips and questions.
Adapted and excerpted from:
D. Oi and P. Koehler, Imported Fire Ant on Lawns and Turf (ENY226), Entomology and Nematology Department (rev. 05/2003).
K. Schofield and B. Drees, "Comparison of individual mound treatments for red imported fire ants, Solenopsis invicta," Integrated Pest Management Manual (2.5MB pdf), Texas A&M AgriLife Extension (2008).
P. Sullivan, "Sustainable Fire Ant Management (CT068)," National Sustainable Agriculture Information Service (2003).
S. Durham, "New Red Imported Fire Ant Enemies in Place for Combat," United States Department of Agriculture Agricultural Research Service (01/2011).