Ask a Master Gardener: Fire Ants

Shown is dodder parasitizing a Hibiscus plant.

Q. Help! Fire Ants are taking over my yard and have moved into my garden. What can I do?

A. The red imported fire ant, Solenopsis invicta Buren, was accidentally brought into the port of Mobile, Alabama, from South America in the 1950s. They likely hitched a ride in shipping crates or similar containers and found the area to their liking. The invaders easily traveled long distances when newly mated queens landed on cars, trucks, or trains, or when winged forms were carried by the wind. Nursery grown stock and soil from an infested area relocated entire colonies to other areas. Besides residing in the Southeast, they are now found in parts of Oklahoma, New Mexico, and Southern California. Along with the red imported fire ant, there are small infestations of black fire ants found in Tennessee, Mississippi, and Alabama. In addition, there are now hybrids found in Georgia as well. Oh Yippee!

Now the bad news — you will not completely eradicate fire ants. You can have success in controlling them, but it takes persistence. Treating a yard and a garden will take different approaches. What is effective in a landscaped area cannot be used in a vegetable garden.

Now, here is some good news. There are many native ants that help control the spread of fire ants as they all compete for food resources and territory. According to the Iowa State University Extension and Outreach, there are an estimated 700 different kinds of ants in North America (north of Mexico). Their Extension Service points out several redeeming qualities of ants: they are among the leading predators of other insects, helping to keep pest populations low; they move approximately the same amount of soil as earthworms, loosening the soil in the process and increasing air movement and water absorption into the ground; they keep the ecosystem clean of dead insect carcasses and aid in the decomposition of plant and animal matter by carrying bits of plants and animal remains into their nests, whereby the soil is fertilized and nutrients recycled through the ecosystem; and lastly, they carry seeds and help plants disperse into new areas. So, don’t hate all ants just because one group is giving you fits.

Your first step to managing fire ants is to make sure that the mounds you see are indeed those of fire ants. So, identify the ants. As you might have unfortunately found, fire ants have a stinger, but most other ants do not. You’re probably not much at trying to get that close of a look, so another way fire ants are distinguished from other ants is by the appearance of their mounds. Fire ants do not have a central exit hole on top of their mound but rather use tunnels to enter and exit the mounds. If you see an ant mound with a central exit hole being used by ants, this is not a fire ant mound. Don’t kill these guys as they are keeping the fire ants out of their territory and your yard.

Once you have identified your ants there are several treatments that you can choose. Managing Imported Fire Ants in Urban Areas: UGA Bulletin #1191 available at https://extension.uga.edu/publications/detail.html?number=B1191#Table1 gives options and methods of treatment for each type of product. If you have less than 20 to 30 mounds per acre, it is suggested that it is best to treat each mound. There are products that are applied as dusts, granules, liquid drenches, baits, or aerosol injections. Always follow the label directions. And yes, drenching mounds with a large quantity of very hot water has been found to be effective. Just use caution and realize that you could also kill any surrounding vegetation and run the risk of scalding yourself.

For controlling fire ants in your garden, you will use different products than those for use in flower beds and turf grass. so always check the label to be sure that the treatment is approved for use in vegetable gardens. These include baits containing the active ingredients spinosad and pyriproxyfen. Spinosad is a natural metabolite product produced by a soil microorganism and affects the ant nervous system. Many of the spinosad products are even approved for organic vegetable production. In addition, baits containing spinosad are relatively fast-acting, making them a good choice for controlling individual mounds in the garden. Pyriproxyfen is an insect growth regulator that mimics the effects of the insect’s juvenile hormone, reducing the production of viable eggs. Although pyriproxyfen prevents the development of more worker ants, it does not kill existing adults. Because of this, ant colonies may persist up to several months after treatment until worker ants living at the time of treatment die naturally. To help keep fire ants out of your garden, treat the perimeter and tackle any mound that is close by as soon as you see it.

As far as biological controls, parasitic nematodes and fungi are still begin evaluated but vary in effectiveness. Those tested caused the ants to move only temporarily. According to UGA Extension Service, the introduction of the natural enemies of fire ants into the United States may someday help to control them, although natural enemies will not eliminate fire ants. In South America, where fire ants have many natural enemies, the ants are still present, but occur in lower numbers. Their recommendation for the best biological control method for fire ants is to preserve native ant species that compete with them for food and nesting sites. One way to preserve native ants is the judicious use of insecticides.

Lastly, a word about all those home remedies that pop up on social media. Gasoline and other petroleum products do kill some fire ant colonies, but these products are flammable or explosive, kill grass and plants around the treated mounds, and pollute the soil and ground water. Applications of vinegar or soapy water may seem to work, but the colony has just moved. And my favorite, feeding grits to fire ants to make their stomach swell until they burst. It is just a waste, as adult fire ants do not ingest food, and the maturing fire ants are only fed greasy or oily liquids. Keep up the fight and be diligent about treating new mounds. You can control these invaders.

If you have gardening questions, contact a Master Gardener Extension Volunteer at the UGA Cooperative Extension Carroll County office at 900 Newnan Road, Carrollton, GA at 770-836-8546 or via email at ccmg@uga.edu.

If you have gardening questions, contact a Master Gardener Extension Volunteer at the UGA Cooperative Extension Carroll County office at 900 Newnan Road, Carrollton, GA at 770-836-8546 or via email at ccmg@uga.edu.

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