Home & Garden

When fire ants invade, tread carefully, and consider these removal tips

A fire ant tops a match in a studio photo.
A fire ant tops a match in a studio photo. NYT

Since moving to North Carolina in 2003, I’ve learned that this state’s gardeners are incredibly hardy souls who tend to persevere, even when conditions are less than perfect for the plants they love. Deer, caterpillars, drought and other obstacles are merely challenges to be overcome. And that’s especially true for gardeners whose purpose is to welcome wildlife.

Still, there’s one garden pest that is being seen increasingly in the Piedmont and has the potential to discourage even the most dedicated plant and animal lover: the fire ant.

Fire ants are South American natives that first appeared in the United States in the 1950s in places like Florida and Texas. They have been traveling northward ever since.

“They were only in about half of Orange County 10 years ago, but now they are everywhere,” said Michael Waldvogel, a North Carolina Extension agent and entomologist.

The species is now found in 74 of North Carolina’s 100 counties – often acting as hitchhikers in fill dirt or balled-and-burlapped plants brought in for new developments.

Personally, I’ve had two close encounters with these invasive creatures over the past 10 years. The result was multiple stings that caused itching, swelling and some pretty serious pain.

I’m a fairly lucky victim, according to Waldvogel. In some people, fire ant venom acts like a deadly poison.

“If you are working in garden, digging into the soil and the ants come boiling out, it might mean a trip to the undertaker – or at least a trip to the hospital,” Waldvogel said. “In some people, the ant bites are annoying, but in others they can have tragic consequences.”

Statistics show about 10 Americans are killed annually by these noxious ants. At highest risk are those whose allergies cause an overreaction to the ant’s venom, resulting in swelling that can block airways. Children and small animals also have higher risks.

Find the ants (carefully)

Identifying the danger is a first stop to avoiding fire ant stings, Waldvogel said.

Fire ant nests are dome-shaped and sandy and can be several inches high. The ants prefer open sunny areas to shade, so they are likely to be found in pastures, ball fields, lawns and even near the beach, where they have been known to prey on tiny sea turtles as they leave the nests. They also seem to prefer to locate next to solid objects, such as wooden posts, concrete paths, stonework or bricks.

“You need to be particularly careful working in a garden, because the ants prefer open spaces,” Waldvogel said. “This is not something you are likely to run into on a hiking trail.”

Although state agriculture rules restrict importation of soil from areas with fire ants to unaffected areas, it still happens – usually unbeknownst to both parties.

“An area might go from fire-ant free one day to ‘Bam!’ they are there,” he said.

Fire ants are active from the first warm days of spring into October or later, depending on the weather. The ants got a slower start this year because of a cooler spring, Waldvogel said.

Rainfall is another factor.

“When we had a drought, it was hard for them to build mounds, and we noticed fewer mounds,” Waldvogel said. “But when we have a decent amount of rain and warm conditions, they thrive, because they are a tropical insect.”

What to do

If you find a fire ant nest in your yard, there are a few possible responses.

Wildlife gardeners trying to steer clear of toxic chemicals may use boiling water to douse the nest – although Waldvogel warns that lugging a big pot of boiling water outdoors poses its own set of problems.

Another tactic involves using a shovel to dig into the nest and fling it – scattering the ants as far as possible. Because they live and work as a colony, this may disrupt the nest entirely, or at least for some period of time.

When Waldvogel finds them in his yard, he jumps on the riding mower and runs over the nest repeatedly until the inhabitants give up and move elsewhere.

In areas with high risk for human encounters, such as a commercial building or a school, it may be time to break out the chemicals. There are several types of baits that attract ants and then kill them, but it is important for gardeners to read labels to make sure these are safe.

Waldvogel points out that the ant mound is like the tip of an iceberg, with a large portion remaining unseen beneath the ground. Repeat treatments can improve the chance that any insecticide will penetrate the nest, reaching the queen and her brood

One recommended treatment is Spinosad Landscape and Garden Insecticide, an organic pesticide judged safe to use on ornamental plants, as well as in fruit and vegetable gardens. The maker, Natural Guard, reports that it’s also relatively safe to use around beneficial insects.

“But it’s unlikely that we’ll ever be able to get rid of them entirely,” Waldvogel said. “They are kind of here to stay.”