No gardener wants to encounter fire ants in the garden, but sometimes we find that they have moved in, unwanted. Getting rid of these pain-inflicting invaders can take some persistence, but options for organic control do exist. Knowing a little about the biology of these ants can help a gardener plan a successful counter-attack.
Fire ants do not tolerate freezing weather very well. If you treat a fire ant mound in fall, even if the whole mound isn’t dead within a few weeks, enough workers can be killed that the rest of the colony doesn’t survive the winter.
In spring and fall, too, most of the ants in a colony will be closer to the surface, so that a mound drench type of product has a good chance of reaching all of them.
In other words, both fall and spring are when organic controls are more likely to work well. Killing off smaller colonies in fall will also reduce the number of new colonies next spring, when mated queens that survived the winter will fly off to start new colonies.
The very first control to try, though, doesn’t use any products at all. On a cool day after a rain (when more ants are nearer the surface), pour a few gallons of boiling water on the mound, starting by circling the mound a foot or so away and then pouring the rest right on the mound. If this doesn’t kill the whole colony, move on to “Plan B”, a purchased mound-drench or a bait. (NOTE: Boiling hot water can burn people when accidentally spilled, and it will also kill plants near the mound it is being poured on. Please handle boiling water carefully, and do not use it near trees, shrubs, perennials, bulbs, or other desired plants.)
Another option is called “bucketing”. You gather up a few buckets, dust the inside with talcum powder or corn starch (to keep the ants in), and on a cool morning dig quickly into the mound, dumping shovels full of dirt into your buckets. Dig deep enough to find the bottom of the mound. Add a generous squirt of dish soap to each bucket, and add water to drown the ants. This works on small mounds, but not on old, deep colonies.
Organic-approved products for killing fire ants typically contain either d-Limonene (from orange oil) or a spinosad compound (from special bacteria) as their active ingredients.
One organic produce that contains d-Limonene, to be used as a drench, is Orange Guard Fire Ant Control. The d-Limonene products have worked pretty well in our area community gardens.
An organic product for fire ant control that uses spinosad as the active ingredient is Captain Jack’s Dead Bug Brew by Bonide. Instructions for using it as a mound drench are pretty far down the label, but they are there.
Whatever product you choose, be sure to follow package directions carefully.
Remember to NOT disturb a mound in any way before using a product on or around the mound. If the ants are disturbed, they go into “defense mode”; a whole lot of ants will boil up out of the mound where they can’t be reached by a drench.
Fire ants are not easy to eradicate, and new colonies will continue to move in from surrounding areas if they can, even when old colonies are killed off. It is their way.
However, gardeners can be persistent, too. Knowing the best times to work on the mounds for best effect helps keep our gardens fire-ant free.
For more information and the recipe for a DIY orange-oil-based soil drench, see Fire Ants in the Garden, Part 2.