Eliminate Invasive Fire Ants

Most ants are beneficial to your garden, but red imported fire ants displace native species and deliver a painful sting.

Ants play a critical role in the ecosystem, both as predators of other insects and as a food source for other wildlife. Their tunneling supplies air, nutrients, and water to roots, and some plants even rely on ants to germinate their seeds. Without ants, your garden, not to mention the greater ecosystem, would cease to function. In other words, the vast majority of ant species do much more good than harm.

The red imported fire ant (Solenopsis invicta, formerly S. wagneri) is an exception. There are native fire ants in the United States, but the red imported fire ant is considered an invasive exotic pest. This South American native has spread around the world in plant material and other cargo. Fire ants are believed to have first entered the southern United States in the 1930s. Today, they’ve expanded into the entire lower third of the country.

Red imported fire ants outcompete native species, sometimes even driving them to local extinction. That’s bad news for the native ants, as well as for the wildlife you want to attract to your garden. For example, in the Southwest, horned lizards feed almost exclusively on native harvester ants. Not only do red imported fire ants displace the harvester ants, depriving horned lizards of their food source, but they also swarm and kill the lizards themselves. Hatchlings of quail and other ground birds, along with newborn cottontails, hares, and deer are also at risk from fire ants.

Learn the difference between invaders and natives.
Fortunately, with some effort and persistence, you can control red imported fire ants. The first step is identification. Red imported fire ants are medium-sized red ants with a darker abdomen and heads that are not wider than the abdomen. You can identify their colonies by their large mounds and swarms of ants that attack at the slightest disturbance.

Make sure that you target the right species. When there are no native ants, fire ants spread more quickly, because they have no competition for their habitat. Don’t spread pesticides indiscriminately across your entire yard, as this will kill all ants and leave you more vulnerable to new infestations.

Control invasive fire ants in your yard.
Experiment with these methods until you find what works best for you:

  • Place commercial granule baits or homemade borax mixtures near the mound. These poison the colony and kill the queen over a few weeks. Be careful to target the red imported fire ant mound, as such bait can also kill native ants and other wildlife.
  • Pour several large buckets of soapy water over each mound. Scalding water will instantly kill an ant. You might need to repeat this process several times before the entire colony is eliminated.
  • Dig up colonies during cold weather and throw each shovelful about 50 feet away. The sluggish ants will die from exposure before finding the colony again. Or dump the soil and ants into a bucket of hot, soapy water. This will weaken colonies, and may even destroy them if you dig up the whole subterranean system.

Stay away from unhelpful control methods.
Pouring grits, Rice, or other grains on a fire ant mound will not kill the colony. It’s a myth that the grains expand in the ant’s stomach and kill it. Also, never pour gasoline, bleach, ammonia, or other chemicals onto the fire ant mound. These liquids are illegal to dump because they are dangerous to people, pets, and wildlife, and they pollute the soil and groundwater.

A Painful Sting

Ants belong to the order Hymenoptera, which also includes wasps and bees. Like their winged cousins, fire ants sting and inject venom that causes burning pain. When the ant stings, it releases a pheromone that tells the rest of its colony to join the attack. For a lizard, a bird, or even a larger animal, hundreds of stings from a fire ant swarm can be fatal. For humans, fire ant stings are typically not fatal, but they are very painful.

Fire ants will swarm if disturbed, so be careful when trying to destroy their colonies. Wear boots and long pants and watch where you step. Smear a few inches of petroleum jelly on the handles of your wheelbarrow, shovel, or other tools.

David Mizejewski is a National Wildlife Federation naturalist and author of Attracting Birds, Butterflies and Other Backyard Wildlife (Creative Homeowner, 2004).