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Fire Ants

March 20, 2018 |

Though their tiny jaws never chop your tobacco leaves, red imported fire ants (Solenopsis invicta) can be a huge pain (literally) as they build their big mounds in greenhouses and fields. Ever since they marched their way across the American South in the 1930s, fire ants have made themselves known with their burning, pustule-forming stings and scrappy attitudes. Most of us only think of fire ants as a nuisance, a danger or as a bit of afternoon fun as we kick over their mounds to watch them boil angrily from the earth. Some of us are allergic to their venom, and all of us find it painful.

Let’s take a second look at fire ants. While bothersome, they have interesting behaviors, and, in some ways, they even give crops a boost.

The Good, the Bad and the Ugly
Fire ants can easily be identified by their giant mounds. Mounds can house as many as 200,000 workers and can be (sometimes much) more than a foot wide and a foot tall. In addition to tipping you off to a danger zone, these mounds represent a lot of soil aerated for your land. Those ants haul up to 10 gallons of soil in their mandibles (that’s what we call ant mouths) to the surface, forming 10 gallons’ worth of tiny, aerated galleries beneath the surface. Their tunnels can span 100 feet underground in all directions, helping them reach water and snacks from the comfort of their homes.

Their mounds have a built-in air conditioning system. Because the soil column gets cooler as it gets deeper, fire ants move their babies and queen up and down the column in their nest throughout the day to maintain a comfortable temperature. If it’s too hot outside, like in the middle of a summer day, everyone goes deep. As the day cools, they pack up their babies and move closer to the ground’s surface.

Sometimes their mounds can get growers’ yields in trouble, as they’ve been reported to nibble plant roots, resulting in lower crop production. Little farmers themselves, fire ants tend herds of aphids like cattle so they can sip their honeydew or snack on their meaty bodies, which can also negatively impact your plants. But they also gobble up plant pests and can keep your leaves clean of caterpillars, stink bugs or anyone else unlucky enough to be discovered by them.

Potato Chip Bait
For those of us less than thrilled with the idea of fostering a fire ant forest in our fields, treating for them can be a cinch. All you need are a few potato chips and some granular protein fire ant bait.
Legend has it that dumping grits on a fire ant nest will cause the little creatures to explode as they gobble up the best breakfast staple. Often, folks report the ants totally gone within a day or two after a grit dump. It’s true that pouring grits on a nest can lead to a vacancy, but grits aren’t killing the ants. Instead, they’re doing what I hope any of us would do if someone dropped a ton of grits on our home: They’re moving someplace else.

Instead of wasting perfectly good grits, try the potato chip test. Place chips around your field to find where fire ants are foraging for food. If you don’t have potato chips, you can use other salty or meaty foods, like tuna fish packed in oil. Wait a half-hour or so after you place your tasty ant snack, then return to see if you have any ant takers. Wherever ants come to your chips, scatter your insecticidal bait. If no ants come to your chips, you’ll know it’s not the best time of day to treat for them. Try another time. This way, you’ll maximize the bait’s effectiveness and minimize the amount of bait you have to use. The most effective fire ant baits are protein, granular baits labeled for crop land like Extinguish ((S)-methoprene).

It may seem logical to cut out extra steps and just dump the bait right on top of the ants’ mound, but just like with the grits, the ants will either just ignore your efforts or move to a new location. They don’t forage for food on top of their mounds, and they see the bait as food.

One last thing to note: Usually, after being hurt by a fire ant, a person will say that the ant bit him or her. Technically, that’s correct. Fire ants do bite. But what hurts most is their sting. They only bite so they can grab on to your skin, making it harder for them to brush off as they repeatedly sting you, injecting the venom that forms those familiar itchy pustules on your skin in a day or so.
From aerating your soil to stinging the tar out of you, protecting your plants to fostering pests like aphids under leaves, fire ants and growers have a complicated relationship. Consider giving them a small “thank you” next time, right before you kick over their mound.

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