Aggressive behavior, crossbreeding are helping invasive fire ants march across NC

AI-assisted summary
• Invasive fire ants, first arriving in the U.S. in 1918, have spread throughout the Southeast, causing problems for residents and farmers.
• Adding to the problem, red and black fire ants are crossbreeding, creating a "super" hybrid ant more resistant to colder temperatures and viruses.
• Local cooperative extension offices and state agricultural departments offer resources and advice on controlling these invasive pests.

What's worse than a small, seemingly unstoppable invader that has already caused headaches across North Carolina for decades?

How about a hybrid version of the little insect with a painful sting.

Since first reaching North Carolina soil in Brunswick County in 1957, the fire ants’ colonization of the Tar Heel State has been all but unstoppable.  Accidental human transportation, a lack of predators, and warming temperatures thanks to climate change − potentially bringing upper elevations in the Appalachians and colder Mid-Atlantic state areas into colonization danger − have helped the insect native to South America spread quickly across North Carolina and the Southeast since the bug first hitched a boat ride to Alabama In 1918.

And now, the two species of invasive fire ants found in the United States are crossbreeding, creating an even nastier and hardier bug.

According to the latest "quarantine" map produced by the N.C. Department of Agriculture and Consumer Services, which requires plant materials like soil and pine straw to be inspected before being transported to ant-free locations, only 23 of the state's 100 counties remain fire ant-free.

"Right now, it just seems they are very adaptable, and that includes moving their nests further underground in the higher elevations where the temperatures are more constant year-round, to some degree outsmarting the environment," said Amy Michael, entomological programs manager with N.C. Agriculture.

Fire ants also are famous for forming into large balls of living matter during flooding events, allowing them to literally float down to new locations. After Tropical Storm Helene dropped record-levels of rain across much of Western N.C. last fall, that ability has officials especially worried about how the natural disaster might have helped the invasive species spread to new areas, said Joy Goforth, plant pest administrator with the state agriculture department.

As they've marched across the Tar Heel State, fire ants have displaced native ant species and caused misery for farmers and suburban homeowners − not to mention some painful encounters anyone who has tangled with a fire ant mound isn't likely to quickly forget.

Their venom, similar to a bee’s or wasp’s, results in a painful, itchy pustule or blister on the skin. Only a very small portion of the population are hypersensitive to ant venom and will experience lethal allergic reactions, according to the Texas Imported Fire Ant Research and Management Project at Texas A&M. Even healthy individuals, however, may experience severe reactions such as anaphylactic shock if they suffer from a multiple stinging incident. 

Treatments for stings are limited, with Texas A&M recommending stings be treated as you would stings of other insects and keep them clean and intact to avoid secondary infections.

Considering a mature colony can include up to 400,000 worker ants, a queen can lay up to 1,000 eggs a day, and that there can be several colonies per acre of land, fire ants can sometimes seem like the perfect pest.

"While eradicating them would be the goal in a perfect world, we really are at the point now where we are trying to manage their impacts and their spread," Michael said.

Do we now have Franken-ants?

Mother Nature has also thrown a new wrinkle into the mix − a new "super" ant that's a merger of the two invasive fire ant species that have reached U.S. shores.

Dr. Scotty Yang, assistant professor in the Virginia Tech Department of Entomology, said hybridized fire ants are the result of interbreeding between red and black fire ants. The outcome is a fire ant that has the strength and ornery disposition of the fiercer red fire ant with the better tolerance of colder temperatures found in black fire ants.

Yang said the hybrid ants have become the explorers and front guard for the fire ant invasion into colder and more northerly areas, becoming the dominant fire ant species in the upper elevations of Tennessee, Georgia, North Carolina and Virginia.

And they are proving to be very successful, with a dozen Virginia counties added to that's state fire ant quarantine map just last year. Yang said viruses that impact "normal" fire ants also have less of an impact on the hybrids, making them less likely to forage and thus less likely to carry poisoned bait back to their mounds.

"In some respect, the viruses help them survive," he said.

Researchers are still trying to determine why the ants decided to crossbreed.

"But once you introduce a species to a new place, anything can really happen," Yang said.

Living with fire ants

After more than 60 years in North Carolina, officials stress that it’s no longer a question of eradicating the invaders, but managing them as best we can. 

Still, as dire as the situation sounds, officials say residents and farmers have options.

Michael said several fire ant control measures are available at garden and home improvement shops, with the best strategy one that targets different stages of the ants' and colony's development − especially treatments that allow bait to be brought back into the mound.

Treating mounds when they appear quickly, especially those near concrete and brick walls where heat radiating from those materials allows the ants to stay active longer, also is important for good control.

Officials stressed that local cooperative extension offices also are great sources of information and advice for homeowners and farmers on the best ways to control the biting invaders, and the state agriculture office also aggressively works with the plant and construction industry to help stop any accidental transportation of the ants to new locations.

"Yes, they are very adaptable, and yes, they can spread pretty quickly," Michael said. "But there are tools out there that are available to residents and businesses to help try and mitigate the impacts and their spread."

Reporter Gareth McGrath can be reached at GMcGrath@Gannett.com or @GarethMcGrathSN on X/Twitter. This story was produced with financial support from the Green South Foundation and the Prentice Foundation. The USA TODAY Network maintains full editorial control of the work.