Anyone with a garden or yard recognizes the mound of a fire ant: tilled-up areas of dirt a foot-and-a-half wide and several inches tall. They house thousands of worker ants and multitudes of reproductive queens. Winged females rise to the top of the mound, take flight, mate with short-lived males and start new colonies wherever they land.
Over the years, I've lost countless melons to fire ants. Seedlings are often upturned and buried by ants forming new mounds in my raised beds. I've replaced light switches fouled with their carcasses and had to roust them out of buildings and my greenhouse routinely. I've been awakened in my bed by fire ant bites on my face whenever they've invaded my house.
In the past, I hoped that researchers would find a way to eradicate the species. Now I concede that we have to manage the problem and try to mitigate its harm to wildlife and food production. The question is, what do you do about them?
Fire ants are a manmade problem and require a manmade solution. I abandon my usual natural approach and follow the example of industrial agriculture.
Online gardening forums are full of natural methods, such as boiling water, corn grits and other measures that are about as effective as wishful thinking. This is one area in which I abandon my usual natural approach and follow the example of industrial agriculture. Fire ants are a manmade problem and require a manmade solution.
Taking the Bait
In 2010 and 2011, I applied Award, a chemical solution from Syngenta. I was reluctant because Syngenta is heavily invested in GMO technology, which spreads more agricultural chemicals into our land and water. But I needed to do something about fire ants.
Award is a granular bait product that uses a growth-regulating hormone to disrupt fire ants' life cycle. The active ingredient acts on a handful of ant species; native black ants and wildlife are largely unaffected.
Baits exploit the ants' need to forage. They pick up the bait as food and feed it to the whole mound, queens and all. Slowly, the whole colony is exposed to the active ingredient in the bait, and the ants die off.
A newcomer product is Come and Get It, a bait containing Spinosad, a bacteria-derived toxin that's nontoxic to all but a specific list of insects. Products that contain growth regulators are toxic to some aquatic life, so I've switched over to Spinosad in order to reduce risk to the ecosystem.
Unfortunately, Spinosad was developed and trademarked by Dow. That puts me in the position of supporting a company whose business plan drives agriculture along a GMO path I oppose.
Baits can take days, weeks or months to show results. Sometimes, I need a faster knockdown when fire ants invade my garden, home or cats' abodes. In these instances, I drench the mounds with orange oil.
My solution is two ounces of orange oil per gallon of water. I mix it up in a five-gallon bucket. Onto each mound, I pour enough of the mix to make the top of the mound cave in and fill up all the tunnels the ants have dug.
Baits can take days, weeks or months to show results. Sometimes, I need a faster knockdown. My solution is two ounces of orange oil per gallon of water.
I also make sure to pour the solution around the outer perimeter of the mound. It takes a gallon or two per mound, depending on its size. The results are immediate. The day after an application, all ants are usually gone.
Alternatively, Monterey Garden Insect Spray with Spinosad may be used for a mound drench, according to its label. It takes about the same amount of solution per mound, but the cost is a little cheaper. Results are not as fast as with orange oil, though.
Fungus and flies
If I need to protect a shelf of seedlings in my greenhouse or a ripening melon out in the field, I use diatomaceous earth. Its microscopic shards of silica keep ants away. If they try to crawl through it, diatomaceous earth will kill them with death by a thousand pricks.
But diatomaceous earth becomes harmless if it gets wet. It's useless as a general fire ant control even if sprinkled directly on the mound, because worker ants enter and exit through tunnels that extend some distance away from the visible part of the mound. It's best used to create a barrier to ants wherever it's sprinkled: shelves, window sills, doorways.
Other techniques for fire ant control include beneficial nematodes, certain fungus strains and a fly that decapitates the ants. The nematodes have not worked for me, and research into other natural controls is in its initial stages.
Using a few bait products and drenching mounds with an orange oil solution, I've gotten fire ants under control. Where it was previously impossible to sit anywhere outside, I can now sit on the ground to watch a meteor shower with only an occasional rogue fire ant attack. What's more, mounds are hard to find; I really have to search to find them.
Since 2011, fire ant activity has declined without my having to do additional applications. A drought may have helped. But the reduction also seems to be in proportion to how much I've increased the diversity of plants and animal life.
I've added more compost to my soil and seen plants thrive. I've planted more variety of crops and flowers and watched native pollinators flourish. I've also seen a noteworthy population of native ants take up residence among my fruits and vegetables, which is a good sign.
Because I do not use harmful chemicals on my crops, I've given insects, animals, microbes and fungus a chance to get established. Once these beneficial species prosper, they seem to make life harder for the fire ant: turning the tables on them, competing for the same food resources and sometimes making meals of the ants themselves, as armadillos have been reported to do.
Perhaps the best hope for long-lasting management of the fire ant lies in bolstering the ecosystems where we live and grow our food.