Fire ants are no mere annoyance—as anyone who has accidentally stepped on one of their mounds will tell you, a fire ant's sting can be painful for weeks. Gardeners who have tried to eliminate fire ant colonies know there is no shortage of advice on how to get to rid of the mounds, but few truly effective methods. But does that mean you need to turn to a toxic solution? No, says Dr. Sanford Porter, a researcher at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida, who has studied fire ants for more than a decade. Here is Dr. Porter's assessment of the many nontoxic methods gardeners' try to get rid of fire ants.
Bucketing fire ant colonies
This is one of the simplest ways of dealing with one or two problem colonies. Basically, the procedure is to rapidly dig the mound and a foot or so of soil under the mound and dump it into one or several large buckets. Sprinkling the bucket and shovel with baby powder or cornstarch before you starts keeps the ants from climbing out of them. Remember to tuck your pants into your socks to keep the ants where you can see them.
Dig up the soil at a time of day when most of the colony is in the mound. In the spring, the best time is usually mid- to late morning. In the summer, it might be early morning.
Once the ants are in the bucket, you can choose to drown the ants or simply to carry them to some place where they are not a problem. If you choose to drown the ants, add a generous squirt of dish soap, water from a hose, and stir to mix the soap throughout the mud in the bucket. The soap breaks the surface tension and drowns the ants much more quickly. It usually takes overnight to kill the ants. In the heat of the summer, they will probably drown faster, but on cool days in the spring, it may take longer. It is best not to fill the buckets more than three-quarters full of ants and dirt so there is room to add the water.
Pouring hot water on the mounds is effective and environmentally friendly, but may require 3 or 4 applications to kill the colony. Water should be at least scalding hot, but does not need to be boiling. This works best when you use 3 to 4 gallons of water in each application. WARNING: Hot water kills grass and shrubbery and may cause severe burns if spilled.
Ineffective. The theory is that the fire ants will eat the dry corn grits, drink some water, and then die as the corn grits expand inside them. The image of greedy little ants exploding like popcorn inside their mounds is very compelling. The problem is that fire ant workers only drink liquids; they are incapable of ingesting solids. Fire ant larvae will eat solid food, but they chew it up and mix it with saliva just like we do before they swallow it. Grits simply don't work, so any perceived effects are due to mound disturbance and colony movement. (Don't look so skeptical—it's true!)
Ineffective. See corn grits above.
Little crystals of silica are supposed to scratch the ant's cuticle so they dehydrate and die. Indeed, if you take a colony of ants and shake them up in bag with diatomaceous earth, about half die. But when you use it on ants outside they usually find ways to avoid it so not many ants are killed. They will not eat it in food and foraging ants do not track it into colonies where it might kill the queen or young fire ants.
Mixing different colonies together
The idea is that workers from the two colonies fight until they kill each other. Workers from two single-queen colonies will fight if they are mixed, but it will rarely result in both or even one colony being killed. However, if you mix fire ant colonies together with multiple-queens in them, it only makes for a bigger party.