[Annual Ant Control Issue] Another Man-Made Ant Pest

More and more ant species are becoming pests of structures. It seems a new species is “popping out of the woodwork” every year — whether it’s the odorous house ant (OHA), the tawny crazy ant (also known as the Rasberry crazy ant), the ghost ant, the white-footed ant, etc. Is this phenomenon a result of urban sprawl (man invading the ant’s natural habitat), invasion by foreign ant species, “global warming” or some combination of factors? Probably the latter!
 

Odorous House Ants.

The odorous house ant is relatively small (workers are 1/12 to 1/8 inch long), and brownish black in color. A distinguishing characteristic is the front of the abdomen overhangs and hides the flattened petiole (waist) of the ant. True to its common name, this ant also gives off a pungent odor when crushed or disturbed.

Although originally a forest-dwelling ant, it has adapted to living in urban areas, where it feeds on aphid honeydew as it does in forested areas. Ultimately this ant adapted to living indoors, nesting in walls, underneath floors and around foundations. In this process, it went from being a single nest and a single queen colony to becoming a large colony with many connecting nests over large areas and sometimes thousands of queens.

Where the process of urbanization has resulted in the loss of many ant species (from 28 to 18 species in our research) as a result of habitat and food destruction primarily, OHA has not only adapted to the urban habitat, but has flourished to the point of overwhelming other ant species, resulting in the loss of 11 additional species (from 18 to 7 species in our research).

We feel that OHA is representative of many, if not all, of the new species that we see “popping up” in urban settings. All of these “new” species have multiple nests with many queens, and some of them reproduce in such large numbers (as a result of many queens) and cover such large areas (with many nests) that they are overwhelming in many ways (outcompeting other ant species — and other animal species).

For example, the tawny crazy ant is an invasive species (from Argentina and Brazil) that has become incredibly abundant and in some areas has not only eliminated fire ants, but also many other insect and arthropod species. As a result, the management strategies and techniques we have found useful for OHA should also be useful, in most cases, for tawny crazy ants and the other multiple queen, multiple nest ants.
 

How Do We Stop Them?

Ants with large colonies, many ants and large number of queens (to keep reproductive rates high) have adapted well to urban and industrial settings. So whether it is OHA, fire ants, Argentine ants or some other ant species that has adapted to man-made environments, they have similar behaviors and lifestyles, and invade our living areas for food, water or harborage. By correcting factors that allow these ants to invade our yards and structures, the first steps in an IPM program will have been accomplished.

In addition to what the PMP implements in the IPM program, the assistance of the customer in excluding ants from yards and buildings is critical. Educate the customer on how to reduce or eliminate the food, water and harborage needed by the ants. Common sense sanitation practices, including elimination of clutter, excess vegetation and junk piles, along with exclusion (sealing all cracks and openings that ants can use to gain entry into structures), will assist the IPM program greatly.

As with all IPM programs, a thorough inspection program is essential in gathering the information needed to make decisions on the management (treatment) plan. Identify the ant species involved, where the ants are active and where nests are located, and conditions that are conducive to ant activity. A plan of action can be designed to eliminate the sources of the problem (multiple nests) and factors contributing to ant success within the multiple habitats they have invaded (sanitation and avenues of access into buildings). This process will also help in preventing future infestations.

Sanitation outside the structure will assist your management goals. Clean up garbage and trash storage areas, and eliminate wood and rock piles, as well as cluttered areas. Inspect patio furniture, play equipment and other items in the outdoor environment. Also inspect mulched areas, shrubs and trees, etc., that may attract ants or provide harborage or access to the structure. Be aware of insects that produce honeydew that provide an excellent source of food for ants.

In using baits and sprays for ant control, be sure to use a non-repellent product to treat as many nests as possible. Treatment zones on and around the foundation are useful in keeping ants from entering the structure. Place baits as close to nests as possible to make sure baits get carried into the nests. Ants entering a structure are looking for food or moisture, as well as places to establish new nests in wall voids, under foundations and other areas.

Baits are best for indoor use; they do need to be strategically and frequently placed so that the worker ants will be successful in getting the bait back to the nest where the queens and young ants are located. Slower acting baits are essential in getting the bait to the nests, whether they are indoors, outdoors, or both.

OHA and other ant species that have multiple nests and many queens are indeed challenging, especially when a colony may extend across multiple properties. For this reason, a regular service/inspection program is needed to ensure long-term ant management.

The authors are with the Center for Urban and Industrial Pest Management, Purdue University.