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Least-Toxic Control of Fire Ants Choose a different pests

Identification

Pest type: Insects

There are a number of different species of fire ants found throughout the U.S. Four species are native to the United States, while two non-native species, the Red Imported Fire Ant (IFA) and Black IFA are spreading rapidly and considered the most aggressive fire ants.

Native U.S. Species

Solenopsis aurea. “Golden Fire Ant.” This ant generally exhibits a light reddish/brown, almost golden color, and may have brown blotches; primarily located in the desert Southwest. The species can often be found nesting under rocks.

Solenopsis amblychila. “Desert Fire Ant.” This ant has a very similar appearance and distribution to the Golden Fire Ant. It is often found in high elevations, over 5,000 ft. They can often be found in overwatered lawns in urban areas.

Solenopsis geminata. “Tropical Fire Ant.” Reddish brown ant found throughout the U.S. south; can be different to tell apart from the Red IFA. Produces a powerful sting. Nests in open fields in sandy hollows, but can also nest in odd areas like rotting wood.

Solenopsis xyloni  “Native Fire Ant.” This ant is widely distributed throughout the Southeastern United States, from California to North Carolina southward. It is shaded dark, but can also appear with two-colored with a red head and black abdomen. It is aggressive and its bite causes a painful sting. This ant is known to loose dirt mounds in grassy, open areas like lawns.

Non-native Species

Solenopsis invicta. “Red Imported Fire Ant.” The most notorious and well distributed of the fire ants, implicated for most stings and infestations due to its highly aggressive nature. Native to South America but imported through shipping routes into the US in mid 1900s; found to colonize most of the Southern U.S. Appears reddish brown, with colors that can vary, but are generally darker than other native fire ants. Produces mounds that appear freshly tilled; thrives in urban and suburban areas. Confirmation of RIFA can be conducted by disturbing mounds – if half of workers in a disturbed mound are large and dark while the other are smaller, it is RIFA, otherwise, if only a few large ants appear alongside mostly small ants, it is likely another species.

Solenopsis richteri. “Black Imported Fire Ant.” Once thought to be a subtype of RIFA, but now classified as a separate species. Very dark, black/red in appearance. Presents similar concerns to RIFA and is known to hybridize.

Wasmannia auropunctata. “Electric Ant” or “Little Fire Ant.” This is the smallest of the fire ants, measuring roughly 1.5 mm long; golden brown in appearance. A native to South America, it is intolerant of colder climates, but has been found to be widely distributed in Florida.

Is it a problem?

Fire ants can produce a powerful, painful bite that can pose risk of infection. RIFA are very aggressive and will confront any human or pet disturbing its mound. They will often outcompete native ants, and can cause ecological damage, attacking the eggs of birds and reptiles, and have even been known to kill fawns and other small mammals. Some colonies can have multiple queens, and queens can lay hundreds of eggs a day. And colonies can travel widely, creating new mounds nearby within days, or sometimes even hours. Fire ants can even survive floods by joining together and creating a "raft." In areas where people may be exposed, intervention should begin as soon as possible after detection.  

Pest prevention practices

Remove food sources
Remove potential habitat
Remove clutter
Foster natural resilience

In fire ant-prone regions of the country, to prevent fire ant infestation into lawns and landscapes, keep a healthy, organic lawn. Fire ants like to colonize bare patches of turf, so management techniques that utilize core aeration to break up soil and improve compaction and pore space, proper watering, and regular overseeding with the correct grass seed can help fill in spaces that may otherwise become occupied by fire ant mounds.

Eliminate any brush or debris around the yard that could provide habitat for fire ants. Remove any food sources that may draw fire ants to your yard, including ripe or fallen fruits from trees, and make sure your outdoor trash can has a tight-fitting lid.

Monitoring and record-keeping

Regularly check your yard for the presence of fire ant mounds. Quick intervention can prevent the spread of the species to other areas or your yard, or to your neighbors.

Non-chemical and mechanical controls

Flame treatment
Boiling water
Aerate soils
Remove debris and habitat

Boiling water can be used to drench individual fire ant mounds. This can be followed up by digging up the mound with a shovel (use protective clothing; be extremely careful and if concerned about bites do not attempt), or dusting diatomaceous earth over the colony. This technique should be considered as part of an integrated approach utilizing least toxic and biological controls.

Biological controls

While researchers and U.S. agencies continue to experiment with biological predators such as decapitating flies, and microsporidia parasites, no commercial available biological controls are currently effective against fire ants.

Least-toxic chemical options as a last resort

An integrated approach to fire ant management is likely to achieve the best results. Use of a boric acid baiting system targeted around the mound, rather than broadcast application of a synthetic insecticide, can achieve fire ant knock down. Past research from USDA (see page 3-4) indicates that solutions of 1% boric acid can achieve 90% colony reduction. Many common boric acid baits on the market will contain higher levels of boric acid (usually around 5%). The problem with this concentration is that it will kill ants before they are able to get it to the queen. The more diluted amounts will allow the ant to survive long enough to share the bait with the queen and rest of the colony. Sugar or greasy food integrated into a 1% boric acid mixture in a bowl or even a soaked paper towel placed near a colony will cause them to swarm the bait and hopefully bring it back to the queen.

If this is not feasible, spinosad is an organic compatible insecticide that can be used, but this is one of the more toxic organic materials on the market. If employed, we strongly suggest only applying it in and around the mounds, and not broadcast applying the product.

A quick note that these baits are unlikely to work if fire ants are not actively foraging. You can place some food by the mound to make sure they are. Boric acid baits should be replenished about once a week for roughly six weeks. 

The next part of an integrated approach is to address individual mounds, generally after at least several days of letting baits do its work. As indicated above, you can drench the mound with hot, boiling water, dig up the mound with a shovel (again, be very careful!), or dust diatomaceous earth over the colony.

You may also want to consider using the least-toxic insecticide d-limonene and gauge its effectiveness. This product is applied by saturating the fire ant mound. The Organic Materials Review Institute (OMRI) lists two organic compliant products to manage fire ants—Antixx Fire Ant Bait containing spinosad, and Orange Guard Fire Ant Control containing d-limonene.

Chemicals to Avoid

Look at your product labels and try to avoid products containing those chemicals listed below:

(A = acute health effects, C = chronic health effects, SW = surface water contaminant, GW = ground water contaminant, W = wildlife poison, B = bee poison, LT = long-range transport)

Acephate (C, SW, W, B)

Bifenthrin (A, C, SW, W, B)

Clothianidin (A, C, SW-URBAN, W, B)

Cyfluthrin (A, C, W, B)

Cypermethrin (A, C, W, B)

Fenoxycarb (W)

Hydramethylnon (C, W)

Imidacloprid (A, C, SW, W, B)

Methoprene (W)

Permethrin (A, C, GW, W, B)

Pyriproxyfen (C, W)

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