As a midwestern gardener, I never had to face many of the challenges intrinsic to deep south gardening, including the problem of fire ants. In our yard they seem to favor sheltered spots, e.g. near paving, tree roots, and in raised beds or other structures, such as our compost bin.
Since I use organic methods I won't use poison bait, and the method I've settled on for now is pouring boiling water on the mound. There are drawbacks, the first of course being that it requires large quantities of boiling water and it's dangerous to carry full pots around for any distance. It also kills not only the ants, but any plants, other animals, and soil organisms in the immediate area; you may have a spot of dead grass for a good while (i.e. months) afterwards. This method is documented as being about 60% effective; keep in mind that chemical controls are only about 80% effective. My experience has been that the first round of boiling water may not disperse the colony. They sometimes rebuild in the same spot or a short distance away (though it is almost always a smaller colony than previously).
Another remedy I've read about that sounds promising is the use of citrus peel derivatives (containing d-limonene), which I've read breaks down the ants' exoskeleton. My concern at this point is that I don't know how it affects other insects and plants. There is at least one commercial product containing d-limonene, and there are recipes for making a home brew. You can download a 2002 Review of 'Organic' and Other Alternative Methods for Fire Ant Control from the Texas Imported Fire Ant Research and Management Project at Texas A&M.
Previously, I've also had some success with simply disturbing the mounds. I had a smaller colony of fire ants in the compost a number of months ago, and with regular turning the ants eventually packed up and moved elsewhere. The colony that's there this time seems bigger and more determined to stay. I've used boiling water on them once, reluctantly, since I didn't want to kill the bacteria in the compost, but as it turns out it had no substantial effect on either the compost or the ants.
What's your preferred organic control method for fire ants?
A friend writes “Have you tried boric acid solution on the fire ants?” I haven’t, and good question. I reviewed Texas A&M’s organic control methods, and they write that “organic gardeners feel that boric acid should not be used outdoors since it can be toxic to plants.” That’s probably why I hadn’t tried it, but I wasn’t consciously aware of the toxicity of boric acid.
Hi! I’m a new reader (found you by googling for the mobile farmer’s market) and so am so HAPPY to have found this blog!
We’ve had a horrific infestation of fire ants inside our house since Gustave’s rains came. What I ended up doing (after the second night of them eating me and my two year old alive at night — we cosleep) is to put a small bowl of boric acid and honey water in the closet (my son CANNOT get into this area). Voila! The reduction of fire ants in our house since is dramatic.
Outside, though, I let them be. But I haven’t started gardening yet (tried and failed last year, and am contemplating starting a winter garden in the next few weeks…) so I don’t know what I would do if there were any mounds in an area where my son normally plays, or I’d be gardening…
This is a great resource, thanks so much!
Hi, thanks for visiting. I’m glad you solved your indoor ant problem. But yes, the garden. Sigh. Inevitably there will be ants. If it’s a small mound I live with it. If it’s a big one, which has happened a couple of times, I use the boiling water. So far I haven’t had any problems with killing plants or harming the soil (in the beds). Bill Finch says just take a shovel and spade in deeply to disturb the mound. Obviously boiling water isn’t safe around kiddos so I only use it when I’ve got someone around to watch my daughter or she’s out of the house.
Don’t let the ants stop you from gardening!