(Editor's Note: This article was originally published on April 12, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
What's so terrible about this little ant? Well, to start with, they are incredibly aggressive. Disturb or (heaven forbid) step on one of their mounds and you will quickly be under attack.
The nasty nature of the imported fire ant is damaging both ecologically and economically. The FDA estimates that more than $5 billion is spent annually on medical treatment, damage, and control due to fire ant infestations. The ants cause approximately $750 million in damage annually to livestock and crops.
The red imported fire ant (Solenopsis invicta) is present as an invasive pest in many areas of the world, including the U.S., Australia, the Philippines, China and Taiwan. It came to the U.S. in the 1930s by hitching a ride on a Brazilian cargo ship that landed in a Mobile, Alabama port. The ants have since spread to most areas of the Southern and Southeastern United States.
Residents of infested areas of the country are all too familiar with the emergence of this pest. After a heavy rain, countless fire ant mounds will rise to the soil surface and dot the landscape. This is a result of worker ants' need to move the temperature -sensitive young ants up high when conditions are wet. When the ground is dry, they move the brood deeper to more humid chambers and you may see no mounds at all...although the ants themselves are still there. Mounds can extend as much four feet below the surface.
No doubt about it, if you are ever bitten/stung by a fire ant, you won't forget it. Fire ants are different from other ant species in the way they bite you - first they chomp down with their mandibles just to get a good grip, then they sting. And they sting repeatedly. The feeling is comparable to being burned with a cigarette...excruciating.
Each bite/sting will form into an itchy, painful, pimple-like pustule. Scratching can cause an infection, so try to resist the urge. Hydrocortisone creams will help sooth itching. Some have reported that dabbing Listerine on bites will sooth itching and pain.
Severe allergic reaction can also occur, especially in the case of multiple stings. Be mindful of any unusual symptoms - like excessive swelling, difficulty breathing, etc. - following a sting. If these occur, head for the hospital.
In gardening terms, these little beasts are not easy to control. Here are some tips:
First, assess the extent of your fire ant problem. Are there mounds all over your yard? Is it impossible for you to dig anywhere in your garden without getting swarmed? If so, I certainly sympathize.
A widespread fire ant problem needs to be dealt with immediately. You'll want to purchase a large amount of fire ant bait and broadcast it over your property with a spreader. Make sure the weather is dry and will remain dry for the next several days.
The best bait products I've found also happen to be organic: choose any bait product containing the natural biological control called Spinosad. This product - sometimes also packaged under the name ‘Conserve' -- was originally marketed as an organic worm and caterpillar control, but shows great success in killing fire ants as well. It is not dangerous to plants, pets or people and is available in either granular or concentrated liquid form.
For those with either a widespread or just occasional mound problem, applying Spinosad bait directly on and around each mound is a good idea too. The idea is for the worker ants to take the bait down into the ground to the queen ant. Once she eats it and dies, the rest of the mound's population will eventually die as well.
A canister of Spinosad containing 16 ounces of dry granules will cover 22 individual mounds or up to 10,000 square feet. Use about 4 tablespoons for each mound. If you are applying with a broadcast spreader, use 3/4 of a cup for each 1,000 square feet. If using a liquid product, follow the directions on the side.
However, a problem remains in that some mounds can contain more than one queen. Therefore, you must be diligent in your bait application, which can take about six weeks to start working. A drench of orange oil on each mound is also a good follow-up. (Texas A&M researchers affectionately call this the "Texas Two-Step" method.) Some folks pour boiling water over mounds, but this technique is a little dangerous and doesn't guarantee the death of the queen(s). It'll kill everything else in the vicinity, though...including your grass.
Ignore the folksy recommendations about applying grits, rice, aspartame, or instant oatmeal to mounds. Take it from somebody who's tried a lot of weird methods: these don't work. The colony may get annoyed and move, but they're still there.
Scientists are working tirelessly to develop a specific species of Phorid fly called Pseudacteon. These little predators have a grim but helpful habit: they live to frighten and kill fire ants. After a Phorid fly lays her eggs in a fire ant, the emerging larvae makes its way into the ant's head and then proceeds to eat out the inside of the head. Eventually, the head falls off and out comes a new fly. Sounds like either a horror film or some perverse torture method from the Dark Ages, doesn't it?
Tallegeda County in Alabama and some areas in Texas have already seen populations of the phorid fly begin to flourish. While it may not wipe out the imported fire ant problem, the emergence of the otherwise harmless Phorid fly is definitely a step in the right direction.
Visit the Texas Imported Fire Ant Research and Management Project web site to learn more.