Most Wanted: White-Footed Ants

These arboreal ants often nest in trees and bushes where they farm (or tend) honey-producing insects such as aphids and scale. They are common on nectar-producing plants, such as gingers, Ixora and orchids, in the subtropical Florida landscape, and have been found in mulch and ground nests as well. Unfortunately, they often take up residence in walls and ceilings once they enter a structure in search of food.

PMPs have learned that ordinary methods of ant control do not work well on white-footed ants. Most ants and many other social insects share fluids from their digestive tract through a regurgitation process called “trophallaxis.” Such sharing does not occur in white-footed ant colonies. This explains why most baits are only partially effective — the ants must eat the baits directly to be killed or affected by them.

Behavior helps their cause

Several other attributes contribute to the successful establishment of white-footed ants in urban environments and the difficulty in controlling them:

• established colonies may contain well over a million individuals, an impressive and exceptional size;
• about half of these individuals are sterile female workers, while the other half are wingless males and females capable of mating and producing fertile eggs;
• winged males and females are also produced, and nuptial flights occur at various times of the year;
• the budding process can lead to the start of new colonies. With multiple queens commonly included in the colony, the reproductive potential is phenomenally impressive.

Florida PMPs who have been most successful in managing this ant species use an approach that incorporates not one, but several techniques. Preventative measures include caulking possible entry points, pruning tree branches and shrub foliage away from the structure and teaching homeowners to eliminate ant access to sweet food sources inside the home through proper sanitation.

Outside the structure, potential food sources must also be eliminated by controlling aphids, soft scale and whiteflies that produce honeydew on the landscape plants. White-footed ants will nest happily in fallen leaves, dry pine needles or even compost piles, so it is important to remove these materials when they are near the building. Liquid baits are used heavily, especially on the outside of the structure, to help draw the white-footed ants out of the interior. Because there is no food sharing among colony members, baiting alone will give only some temporary relief. The ants don’t accept solid baits at all, which limits the selection of materials.

An effective residual chemical barrier applied as a full coverage perimeter spray is a critical component in overall white-footed ant management. Many large pest management companies have achieved success using a long-residual liquid formulation of bifenthrin.

What have we learned from our experience with white-footed ants over the past few years? First, we have to admit that although we can control these ants with a multi-pronged approach, we will probably not be able to eliminate them completely. Then, combining a regular monitoring program with mechanical and sanitation techniques, systematic baiting and spray application will ensure that the white-footed ants remain under control and out of the buildings we’re hired to protect