Fire Ants - Control Methods

Spring is officially 48 days away. I started my pre-season cleanup this weekend, cutting down dead grasses and decapitating spent perennials. I spread a little bit of mulch across the surfaces of some containers, and found the location where fire ants overwintered here at New Hope Farm – IN my mulch pile. Fortunately, the cold temperatures slowed them a bit, and I managed to escape with a single bite.

Fire ants are found in more than half the US now, across the south and up both east and west coasts. That means a lot of gardeners are preparing to do battle with these tiny warriors.

However tempting it is to stir their mounds and watch them scurry around, disturbance does little other than send them deeper underground or make them dig new tunnels a short distance away.

Here are a few common but erroneous  beliefs:

Theory: Grits will kill fire ants.  The idea is that fire ants will eat the grits, which will then magically swell inside their stomachs and cause them to explode. An entertaining thing to imagine (especially if you have just been bitten), but wrong.  Fire ants do not eat solid food.  Instead it is transported to their larvae where the larvae use digestive juices to break it down into a liquid form. It is then distributed to the entire colony.  Sprinkling grits around fire ant mounds actually provides food for them.

Theory: Boiling water kills the mound.  Boiling water will kill almost any insect it touches. University of Arizona says the extensive tunneling can reach 7 to 10 feet below the surface, depending on soil type.  They are deepest in clay soil.   Two problems with this method are: 1) Water will not penetrate the entire mound and kill all the queens and eggs, but will kill all plants and microorganisms in the soil. 2) Personal safety of handling and transporting gallons of boiling water to each mound. 

Theory: Pour enough water on them to drown them.  The difficulty is getting enough water to saturate the entire mound long enough to suffocate the fire ants.  Also, many of the ants may be flushed out of the mound alive, making this method ineffective too.

Theory: Gasoline or kerosene will kill them.  Three problems here. 1) Like water, above, it is virtually impossible to apply enough to penetrate the entire mound, 2) It is illegal to pour fuels and solvents onto the ground due to groundwater contamination.  This is a criminal act in most states and can result in fines up to $thousands per day.  3) All mounds have a small but open channel directly to groundwater. Other chemicals including brake fluids, bleach, household cleaners, etc. will also reach groundwater.  Please, please don’t pour these fluids on the ground..

Theory: Soapy water will kill them.  This approach assumes that soap will break down the waxy coating on their bodies. Thus the ants will be unable to retain water, will dry out and die. While this may cause problems for the ants that experience direct contact, it will not penetrate the entire mound and can cause groundwater contamination. Some cleaning agents may contain phosphorus, which is a nutrient for landscape plants when applied in proper amounts, but will cause prolific algae growth in ponds and lakes, and cause nightmares for your water purification plants.

Theory: Granular laundry detergents will kill them.  This assumes that the fire ants will actually eat the laundry detergent.  The fire ant can smell approximately 5,000 times better than humans, so they will not be tempted to eat  aromatic (or even low fragrance) detergents.  And they don’t munch on Tide pods, either.

The best control for fire ants is properly applied bait or insecticide. 

Fire ant baits must be applied when the ants are actively foraging, and this will only be when the soil surface temperature is between 70 and 95 degrees Fahrenheit.  Even then, bait applied at mid-day or night misses the most active forage times and limits its effectiveness. 

The best times to apply baits are between 7:00 and 10:00 a.m. or between 6:00 and 8:00 p.m.   Always follow label instructions for your chosen product and use the product only where and in quantities specified by the label.

So, for the time being, I'll ignore the ant family living in my cold mulch pile.  But warmer weather is coming, you evil demons. Be prepared.


Sincere thanks go to the various universities that have conducted controlled experiments to debunk these myths.