Herself's Houston Garden

Conservation through cultivation

Fire Ants




I’ve been lucky so far. I wandered into a nest of them once last year and that’s been it so far. Not bad for two years of gardening and wandering through woods and fields.  These ants are terribly aggressive and attack anything vertical that disturbs the mound. The husband ran across an ants nest and wanted me to come look and tell him if they were fire ants. I told him I didn’t have to, since he had not been attacked they weren’t.

Fire ants came from South America to Alabama in the 1930s. They reached Texas in the 1950s and have spread across the eastern two-thirds of Texas.  We currently have four species of fire ants in Texas. ( Southern, Desert, Red Imported, and Tropical ).  The red imported are our biggest trouble makers.

Treatments should be done in late April-May and again Sept.-Oct. If you work with your neighbors and treat the whole neighborhood at the same time you’ll have much more success.  Bait is the most effective treatment we know for fire ants.

The Coop Extension recommends ‘The Texas Two Step Method’ of treatment. They recommend using bait broadcast over your entire lawn. I’m not a fan of broadcasting pesticides, the extension office says there is very little pesticide in the bait and it is safer because it is carried back into the nest. Do as you see fit. Baits should be scattered lightly over the entire area. Bait is only effective when used between May and Oct. when the ants are actively looking for food. Baits work slowly, those containing indoxacarb, hydramethylnon and spinosad work fastest. Still you should expect it to take 2-4 weeks. Use fresh bait, don’t water for at least 8 hours. Bait quickly loses its effectiveness in the heat. This is best done in the spring and fall.

The second step is to directly treat any mounds you find. Apply insecticide directly to the mound. Use one to two gallons of water mixed with pesticide per mound. Otherwise it won’t sink deep enough to kill the queen. Dusts should be poured heavily over the mound, baits can be placed on or near the mound.

It is very important you do not disturb the mound when laying bait.  Not only will they attack you, but they are likely to move the nest and your bait won’t be eaten.  Fire ant mounds are generally out in the open with out a visible opening.

If you are using a liquid pesticide, dampen the area around the nest first.  When the weather is dry they all hide deep in the nest and won’t come into contact with the pesticide.

Fire ants will move into buildings if an area has been flooded, but usually are not found indoors.

I find shoveling the nest out and pouring boiling water soapy water works for me. And you don’t have to dump chemicals everywhere. If you don’t have much of a fire ant problem, I’d recommend treating that way and reserving more serious treatments for more serious problems.

Fire ants love to build nests in pots.  Be very careful when repotting potted plants or when you bring in the potted plants for the winter.  Fire ants also prefer dry areas to damp areas, which is probably why I rarely see them in my gardens.

Fire ants eat ticks and fleas which is why you have so few problems with fleas and ticks down here.

Most importantly it now appears fire ants will not move into areas occupied by other ants.  If you leave the native ants alone, you won’t have fire ant problems.

I’ve been told the Texas Fire Ant population is decreasing, seems one of our native nematodes has developed a taste for fire ants. In case the nematodes in your yard haven’t yet started to attack your fire ants try your local nursery. Many of the larger organic nurseries are carrying non-native nematodes you can spread in your yard to combat the fire ants.

More information:
Texas Imported Fire Ant research and Management Program

Thanks for the image!

Of interest:
Red fire ants facing killer virus
Experimental evidence that human impacts drive fire ant invasions and ecological change
Nematodes grown in cultivation as a pesticide are not as good as ones that develop in the wild