[Ant Control] On the Trail of Ants

In the United States, more than 70 species of ants could be considered pests of structures in one way or another, about 35 percent of these being species of carpenter ants. Most all of these are considered nuisance pests — people just don’t like having them in their homes and businesses. A relative few are destructive (carpenter ants) while others pose a potential health threat through stings (fire ants, Asian needle ants) or by carrying bacteria (Pharaoh ants).

How many various pest ant species a pest professional may encounter depends on geographical region, state or even down to areas of a city. Pest professionals in New England generally deal with one to three species regularly while those in South Florida may encounter as many as 10 or more species in a week. No matter which ant is found on a customer’s property, certain basic strategies, techniques or practices can be used to evaluate and solve most ant issues.

This article will take you on a tour of the United States to examine cases involving common pest ants in different states and, along the way, helpful tips and ant control strategies will be provided and discussed. Ready to start the tour?
 

Massachusetts.

We will start the tour at a home in Massachusetts, a state where the black carpenter ant, Camponotus pennsylvanicus, is a major pest ant invading homes. Pavement ants also are common in this state, but one also may encounter citronella ants, odorous house ants and maybe even the European fire ant in select neighborhoods.

A homeowner tells her service professional about big black ants being seen in her son’s bedroom. What should he do; where should he start? After confirming that, indeed, the culprit is a carpenter ant, the ideal strategy is to find and treat the parent colony, which is almost always located outside in moist, dead wood (tree hole, stump, etc.). This parent colony could survive indoors if a consistent moisture source is present, such as a roof or plumbing leak. Looking for signs of water leaks should be top of mind during the inspection.

In most all cases involving carpenter ants indoors, the ants inside are either foraging from outside (when ant sightings are inconsistent) or more likely from one or more satellite colonies located inside (when ants are being seen daily). Still, satellite colonies connect via trunk trails to the parent colony outside so the best place to start the inspection is outside, not inside.

Start outside by the area of the house where ants are seen. Any trees, stumps or landscape timbers near that area? See any ants trailing on the house? Any signs of excess moisture on the soffits, around windows, etc.? Check the base of trees, stumps and landscape timbers for foraging ants. Carpenter ants forage primarily after dusk and before dawn, so during the day the trails are harder to find.

It can be helpful to put out small piles of granular ant bait or dabs of gel bait where foragers are seen or next to likely sites where these ants might trail. Check these sites after 10 to 15 minutes to see if carpenter ants are taking the bait and recruiting a trail to the sites. An active trail can be followed back to the nest site or to entry points on the house. When a trail heads off in a particular direction, look that way to see where dead wood (trees, stumps, etc.) is located. These are probable nest locations and should be checked for ants.

Use a pyrethrins-based aerosol to flush cracks and voids in soffits, porch columns, tree holes and other sites suspected of harboring carpenter ants. Locations showing ant activity may then be treated using a residual dust product.

Indoors, a stethoscope may be used to listen for nest activity under windows, inside walls, or other voids or wood where ant activity may be suspected. The attic, crawlspace and basement (if present and accessible) should be inspected for signs of moisture and ant activity (frass, dead and live ants). Insulation, especially that which is moist or near water leaks, is a potential nesting site for these ants. Customers also should be asked if they’ve seen piles of “sawdust” that reappear even after being removed.

Carpenter ant nests, once located, are fairly simple to treat by accessing the nest (usually by drilling) and application of a suitably labeled residual dust or aerosol insecticide. A mature parent colony can have up to 12 or more satellite nests, so treatment of satellite nests inside may not stop inside activity if the parent colony re-establishes new satellites indoors.

Ideally, finding and treating the parent colony is the ultimate solution but may be easier said than done. It could be located high in a tree or even on a neighboring property and thus inaccessible. In such cases, baits may be the best option but may require one or more follow-up visits to replenish or replace baits. Treatment of entry points and foundation areas using a non-repellent insecticide (e.g., fipronil, imidacloprid, dinotefuran) has proven beneficial in limiting or stopping inside incursions by carpenter ants.
 

West Tennessee.

The Mid-South area around Memphis is ground zero for odorous house ants (OHA), by far the most troublesome pest ant in the area. Acrobat ants, little black ants and fire ants are also a concern in many areas, but it is the OHA that causes pest professionals the most headaches.

The thing to remember with the OHA and similar tough-to-control species is that they are polygynous (multi-queen) and polydomous (multi-nest sites). These two factors are key to the difficulty in controlling such ants. The numerous nest sites will be scattered around a property and onto neighboring properties serving as reinfestation sources for the property and the building. The multiple queens also contribute to the persistence of these ants.

Most all OHA infestations originate from outside nests and only on rare occasions will an infestation be solely from an indoor colony (e.g., potted plant brought indoors). Start outside along the foundation searching for ant trails — be sure to pull grass and vegetation away from the foundation to check for hidden trails.

In landscape beds, use a probe or hand rake to move leaf litter and mulch around. Such movements reveal colonies within as the ants rapidly begin frenzied activity. It is beneficial to keep a sprayer, containing a properly labeled residual, on hand to treat these small colonies as they are found. Ants quickly can abscond when disturbed, moving the entire subcolony within minutes. Being prepared to treat colonies as they are discovered helps improve the efficiency and effectiveness of the control effort.

From the foundation area, look outward for likely nesting sites. For OHA, these include piles of items, flagstones, leaf litter, potted plants, sprinkler heads, the soil next to trees and shrubs, and even loose bark on trees. Finding and directly treating as many subcolonies as possible is helpful to keeping the ants at bay, away from the structure, thus minimizing the potential for ants inside.

The third point of emphasis is treatment of potential entry points and possibly the foundation itself, if the infestation is moderate, severe or chronic. Application of one of the several non-repellent residual products works well for this purpose.

Last, if needed, application of baits may be included. Usually, baits are employed if the infestation has been difficult to control or is significant in its severity. With multi-nest/multi-queen pest ant species, baits will provide varying levels of success so a combination of the above strategies is important for most cases. Odorous house ants can be finicky so offering a variety of bait products to see which are accepted is prudent. Both granular and gel/syrup baits should be offered and numerous trails should be baited. A single bait placement may only be visited by ants from one subcolony, so any other colonies will not be exposed to the bait. Remember, every trail could be from a separate nest.
 

South Florida.

In the United States, the Southeast corner of Florida is the hotspot for pest ant diversity in the country. The most troublesome ants are found there, including the white-footed ant, Technomyrmex sp.), the African big-headed ant (Pheidole megacephala) and the tawny crazy ant (Nylanderia fulva). Additionally, the Florida carpenter ant, ghost ant, common crazy ant, robust crazy ant, Pharaoh ant, imported fire ant, little fire ant and several others could be encountered at any structure. Some neighborhoods may be particularly troubled with one species (African big-headed ant) and it is not uncommon to encounter as many as four to five or more pest species in/around a single house.

As an example of the strategies for combating the most difficult ant species, we’ll examine an infestation of the tawny crazy ant in a home. This ant may well be the hardest ant to control and, in fact, with many cases, just getting control to the point where the homeowner only sees ants inside on occasion is a challenge.

Let’s start with the biology and behaviors that make this species troublesome. The colonies can be huge, containing hundreds of thousands of individuals spread over a large area, usually extending onto neighboring properties. Trails of foraging workers are persistent, establishing entrenched trunk trails leading to resource sites and buildings. It is not uncommon for these trails to be located subsurface, moving underneath sod through the yard up to and around the house. The worst infestations tend to back up to undeveloped fields or wooded areas. Foraging ants crossing treated surfaces will die in huge numbers daily yet the workers continue to cross along the same spot eventually wearing away the treatment residual. At this point, ants may continue their work unimpeded by the treatment. Subsequent treatments will kill even more ants yet, in severe cases, the piles of dead ants accumulate but the ants keep coming. It is this behavior combined with a huge colony that puts the tawny crazy ant at the top of the “tough to control” list for ants.

As with many pest ants, a multi-faceted strategy is needed to alleviate or minimize a tawny crazy ant infestation. With this species, start with the property perimeter as the main portion or parts of the colony are typically located on neighboring lots. Check the base of trees and shrubs for ants foraging into them looking for food resources. Check for trails on fences, sheds and outbuildings. Look at landscape beds, checking mulch and leaf litter for nests. Turn over stones, investigate piles of items and check the soil at the base of plants for subcolonies. Look under and inside potted plants for ant nests. Treating colonies as they are uncovered is beneficial.

Along the foundation, patios and driveways, use a probe or tool to dig in mulch and soil along the building and pull grass and other vegetation away from the foundation to look for hidden trails or subcolonies. Where possible, pull up the sod where trails are found to see if the trails are originating inward under the lawn. Check window and door sills for foraging trails as well as trails up downspouts and along the frieze board and soffits. Look for cracks, gaps and holes around pipes and cables that may allow ants to gain access.

Infestations of this ant generally cannot be managed successfully without more frequent services than occur with a conventional pest control service (e.g., quarterly). During the height of summer, weekly or bi-weekly services may be needed for the most severe cases. Label constraints regarding treatment intervals and making applications to the far corners of the property can be challenges because control efforts are often needed to the property border (in areas that show activity).

Consult product labels and your state’s regulations to see which residual products may be applied to treat ant colonies far away from the building or to make applications to ant trails on fences and tree trunks. Treating along the edges of sidewalks, porches and patios is helpful for intercepting ant trails — follow the product’s label directions for such use.

Where ants are foraging up into trees or shrubs, placement of ant bait stations containing a liquid/syrup ant bait at those locations pulls ants to these sites, thus introducing the bait into the colony’s food supply. Pest ant species like this one can consume a lot of bait in a hurry so using a station that holds considerable volume (e.g., Antopia) is warranted. When the ants become well-established at such stations, this strategy can pull a lot of foragers away from the trails leading to the stucture. Experience has shown that tawny crazy ant activity at liquid bait stations may lessen over time but typically rarely ever stops. This fact lets us know that despite our best efforts, we never really eliminate the colony but only impact its size and, hopefully, stop interior invasions of the customer’s home or business. The downside of liquid ant bait stations is the need to service them regularly to (1) replenish bait before it is depleted, (2) change baits if ants are avoiding it and (3) move bait stations if ant activity moves to other areas.

On the building, treatment using a non-repellent residual should be made along the foundation following the product label directions. Treat exterior cracks and openings with a non-repellent residual (aerosol, dust or foam). Where ants are invading through windows, consider applying a strip of insecticide using a disposible paint brush to the sill after opening the window. A quick spot treatment with one of the residual aerosols (e.g., PT Phantom Pressurized or PT 221L) is an alternative.

Lastly, plants attractive to homopterous insects (aphids, mealybugs) are important food resources for most pest ant species. Temprid SC is labeled for treatment of plants in controlling ants through systemic uptake by the plans to control aphids and mealy bugs. It is important, however, to avoid applications to flowering plants to help protect bees and other pollinators. Label directions should be followed and some states may not permit such applications under a GHP license. Talk to your local Bayer representative regarding use of Temprid SC for this purpose.
 

Summary.

Each of the above examples provided from around the U.S. illustrate the various strategies, techniques and tips that may be used to control most infestations involving ants. Most inside invasions start outside and very few are strictly indoor issues. Finding and treating the colony, including as many subcolonies as possible, usually provides the quickest control. Baiting is an important tool but reliance on baits alone (except with Pharaoh ants and limited infestations) may provide unsatisfactory results. Likewise, simply treating the foundation and ant trails will kill ants, but colonies may quickly rebound. Problematic pest species, such as the tawny crazy ant, Argentine ant and white-footed ant, require comprehensive efforts employing most of the techniques and strategies discussed here.

The author is owner of Stoy Pest Consulting, Lakeland, Tenn.