Fire ants are a common pest across much of the southern United States. Quite often, they enter structures seeking food, water and shelter. When it comes to treating fire ant infestations for a typical home with a monolithic slab, there is a process that has served me well. Below are the steps I take to combat fire ants in these types of homes:

STEP 1: CHECK THE PERIMETER. The most likely entry point for fire ants is along the exterior of the home. Inspect the perimeter looking for mounds built right up against the foundation and ants trailing into a weep hole between bricks or under the siding. The location of ants on the exterior may not be near where ants are found inside the home. Fire ants are very good at traveling inside walls and under flooring and popping up in seemingly random locations in the house. Once mounds and trails are located, they should be treated directly. Additional treatment to the yard and the interior of the home may be necessary. Follow product labels for application sites and rates.

STEP 2: CHECK THE BATH TRAP. If fire ants are not found on the perimeter, the next place to check is the bath trap. This area is located where bathtub drains enter the floor. Because there is accessible soil in this area, an active mound may be present. Fire ants entering the bath trap also may be found in other, sometimes distant, locations within the home. Treat with a product that will provide a quick knockdown to achieve immediate results. Since fire ants are capable of moving extra soil into this area, this soil should be removed after treatment. If the bath trap is not accessible, an inspection door can be installed with the permission of the homeowner. If not possible, then move on to the following steps.

STEP 3: CHECK OTHER PLUMBING PENETRATIONS. If you don’t have success with the first two steps, things can get more complicated. Locally, we often find fire ants in bathrooms with garden tubs. A garden tub is usually mounted in a corner with two exterior walls. Fire ants enter around the plumbing or bath trap and build mounds between the basin and walls of the tub. In some cases, panels can be removed to allow this area to be inspected and treated. In others, the panels are caulked or the tub is a solid piece that sits on the slab.

If accessible, the ants can be directly treated. This is a good situation to use a dust because it provides long-term control. Always check the label to make sure a product can be applied in the desired location. If this area is not accessible, then the best remaining options are baits and non-repellent perimeter treatments. In both cases the goal is to impact ants from under the tub as they forage out into the yard. Application is most important on the exterior walls near where the tub is located. This treatment may require additional time to be effective, but it will be successful. Baiting on the inside where ants are seen is also an option, as long as there is not a risk to children or pets and the product is labeled for application to that site.

STEP 4. LOOK FOR THE UNSEEN OR UNEXPECTED. If ants are not found in any of the areas discussed previously then it is likely that ants are entering through a crack in the slab or other opening under the walls and flooring that will not be able to be detected. In those situations, I resort to a baiting or non-repellent liquid treatment as discussed in step 3.

This technique was used recently in a home where a wood floor was placed on top of a slab. Boards were glued to the floor several inches apart with the main floor installed over the top of these runners. The very beautiful and expensive wood floor had occasional knot holes that extended all the way through the floorboards. Having exhausted all these ideas, we tried applying a granular bait through the knot holes and were able to control the fire ants. The ants seem to have found a crack in the slab and were actively foraging in the void between the slab and floorboard runners.

FINAL THOUGHTS. Each situation is unique and there certainly will be challenges that extend beyond these steps. Fire ants can be found living in a variety of locations, which adds to the complexity of treating for them. However, one factor in our favor is that fire ants are extremely good foragers and will gladly accept bait placed in active areas. When it comes to fire ants, there really is value to thinking outside of the box and placing bait where the ants will find it.

Bart Foster earned his bachelor of science and Ph.D. degrees in entomology from Texas A&M University and currently serves as training and technical manager of Beaumont, Texas-based Bill Clark Pest Control. Bill Clark Pest Control is part of the Copesan network of local service providers.

Copesan is an alliance of pest management companies with locations throughout North America. To learn more, visit