Where Will the Fire Ant March End?

April 23, 2016 02:22 AM

Invasive pests are a scourge on agriculture

Keep the granule bait close, and the Benadryl closer. It’s a sting that keeps on giving … and hurts like hellfire. A venomous stinger, capable of multiple injections, produces manic bucking and slapping in its victims. The description might seem exaggerated, but the searing burn of swarming fire ants testifies to the contrary.

Invasive fire ants, six-legged devils barely an eighth of an inch long, have become a scourge to farming and livestock production. Arriving on American shores roughly 80 years back and facing no natural enemies, they spread across the entire Southeast and then west to California. Poisoned stings are a genuine nuisance (and can even produce anaphylactic shock), but their true impact is a multibillion dollar slam to the U.S. economy each year, particularly the agriculture industry. The cumulative financial damage wrought by fire ants continues to climb toward shocking totals. In 2006, Texas A&M research estimated fire ant damage to the overall U.S. economy at $5.65 billion per year.

The Midwest has been watching and waiting for years, hoping fire ants would remain confined to the warm, bottom tier of the U.S. Weather permitting, that might be what happens, according to Sanford Porter, a research entomologist with USDA-ARS in Gainesville, Fla. “Fire ants thrive in heat, but die when it freezes,” he says.

Fire ants are notorious for damaging agricultural vehicles and equipment of all sorts. “They’ll haul in dirt and build nests inside the warmth of any type of electrical equipment,” Porter says. “Fire ants get fried when they hit switches and release pheromones causing more ants to swarm. It’s a mess of broken switches, dirt and ill-tempered ants.” 

Raised fire ant mounds are typically 1' in height but can reach more than 2', easily capable of dulling blades or breaking equipment. “I’ve seen pastures with 200 mounds per acre, translating to millions of fire ants. As a producer, that means you’ve got to be on a constant hunt for them,” says Blake Layton, an entomologist with Mississippi State University Extension. They function as half herbivore and half scavenger carnivores, killing small livestock or wildlife, ruining pick-your-own operations and necessitating hay bale quarantines and certification.

Fire ant damage extends to crops, Layton adds. “They sometimes damage corn, soybeans or milo. If you don’t get a good seal on the furrow, they’ll feed on seed and take the germ out. They’ll also girdle the stem of citrus trees, access the sap and permanently damage the trees,” he notes.

As for control? Granular baits at farm scale are cheap and work well but are slow acting, taking two to six weeks to knock out a colony. Layton recommends using a Herd broadcast seeder at 1 lb. to 1.5 lb. per acre. “Some producers add the bait to fertilizer, but that’s a mistake,” Layton warns. “Fertilizer dries out the bait oil, and the ants won’t consume the granules as well.”

Ranging from Virginia to California, fire ants spread roughly 5 to 20 miles per year. There are two species of invasive fire ants in the U.S.: black and red. “We think the blacks came in about 1915 from South America in timber shipments, followed by the reds in 1930,” Porter says. “In South America, the two species don’t interbreed, but curiously, they do in the U.S. The northern halves of Mississippi, Alabama and Georgia are filled with hybrid fire ants.”

Despite demanding farmer vigilance and billion-dollar losses to the U.S. economy, where will their march end? “Is the Midwest safe? Right now, as long as you get ground freezing to a 1⁄2' depth, fire ants don’t do well,” Porter says. “But up the warm coasts? They could reach Delaware in the East and Seattle in the West.” 

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