Ants aren’t going away anytime soon; in fact, new exotic species that could prove to be pests will continue to be introduced into the United States. The top five or seven pest ant species continue to put pressure on buildings and the efforts of pest professionals to control them. Some homes and businesses experience chronic ant issues, peaking in mid to late summer, and require more frequent services. The strategies and methods for managing ant infestations have changed little over recent years, though the list of available products continues to grow.
The following discusses the top tips for dealing with ants in and around buildings. Which tips may be best to resolve an infestation will vary with the type of ant and the situation at hand. It is up to the pest professional to consider which strategies/methods may be best to resolve or minimize the infestation.
START WITH THE ANT. Knowing the identity of the ant involved is important to knowing where to best look for the colony/subcolonies. Big-headed ants, pavement ants and fire ants nest almost exclusively in soil (see top photo on page 36), so look for piles of displaced soil along foundations, in potted plants and on floors along walls. Carpenter ant and acrobat ant nests are mostly associated with wet or rotting wood, but they will nest in any void or between stacked items, especially lumber. Our most problematic pest species, such as Argentine, crazy and odorous house ants, are opportunistic in nest site selection from shallow nests in soil, to leaf litter, mulch, piles of items, voids, sprinkler heads, meter boxes, under carpets and insulation. This factor makes this latter group the most difficult to control as some subcolony nest sites can easily be overlooked, leading to continued infestation.
FIND THE COLONY. The key to control of ants is to kill the queen(s), which is best accomplished by finding colonies and treating each directly, killing workers, brood and queens. With a single queen species like most pest carpenter ants, the best results occur when the parent colony (which houses the queen) is found and treated. Carpenter ant parent colonies are almost always associated with wet wood and are found outdoors — unless a water leak exists indoors.
CHECK OUTSIDE FIRST. Pharaoh ants are the one species where the infestation is most assuredly indoors, but they do spend a lot of time foraging outside the building from interior subcolonies. The carpenter ant parent colony will usually be outside and inside colonies are satellite nests. Species such as Argentine, crazy, odorous house, ghost and rover ants may have a subcolony or two indoors, but most subcolonies will be outside and interior sightings are just foraging workers indoors. When ants are seen indoors, follow trails to locations where ants may be entering (e.g., windows and doors, under walls, cracks in slab). Trails often are found along tack strips under the edge of carpets.
DON’T STOP AT ONE. Few of our pest ant species have but a single colony involved with an infestation. Exceptions may include certain carpenter ant species and acrobat ants. Rover ants have individual colonies but infested properties often have numerous, even dozens, of individual nests. Inspections should not focus just along the building foundation, but also out to the property’s perimeter. With polydomous (multi-nest) species such as Argentine and crazy ants, if nests away from the structure are left undiscovered, they can easily and quickly reinfest treated areas, thus continuing the infestation indoors.
RIGHT FORMULATION OR PRODUCT. Which insecticide formulation is chosen to treat ants depends on the site that is being treated. Ant nests in soil are best treated by drenching with a water-based product, although some residual aerosols allow for injection into soil nests. Ants that respond well to baits, such as fire ants, may have mounds treated with a granular bait.
Carpenter or acrobat ants nesting within wood can be treated with a residual dust or aerosol formulation. Ant nests in a hollow void may be treated with a dust, but voids containing insulation may best be treated with an aerosol for better penetration through the nest. Pharaoh ants are best treated first with ant baits for a number of weeks. Read the product labels and keep different formulations available to deal with any situation.
CARRY YOUR SPRAYER. Ant nests exposed by turning over items or disturbing leaf litter or mulch will quickly abscond and move the colony, often within as little as 10 minutes. Pest professionals should carry at least a hand sprayer or backpack sprayer during ant inspections to immediately drench the nests as each is found (see above photo). Following this practice also saves time as only one trip will typically be needed to most areas of the property as opposed to two trips to inspect then return to treat (with the possibility many discovered ant nests have moved).
ENSURE GOOD DISTRIBUTION. When drenching nests in soil or mulch, it is important to apply enough to penetrate through the entire nest. The larger the nest, the more volume that may be required — large fire ant mounds may take two gallons of treatment to effect thorough distribution.
RAKE BACK MULCH. Where numerous ant colonies are found living within a landscape bed, rake the mulch back to expose the colonies to treatment. Raking causes ant activity which pinpoints where in the mulch each ant nest exists. Mulch can then be raked back into place. Raking also may be needed for piles of leaf litter, although raking it back into place after treatment is not recommended.
NOT JUST PERIMETER. Application of water-based residual sprays to a building foundation is a useful tool for a number of pests, including ants. If, however, a perimeter treatment is the only strategy employed, success in stopping an ant infestation often does not occur, especially with problem species such as Argentine or crazy ants or where a chronic or moderate to severe infestation is encountered. Large ant populations (e.g., Argentine, crazy, white-footed ants) have been known to wear the insecticide residual off treated surfaces, sacrificing thousands of workers, and allowing interior invasion to continue. Additionally, foundations exposed to the sun, rain and irrigation can experience rapidly reduced residual activity leading to ants evading treatment.
The best course for ants is to find and treat the colonies, apply residual treatments along active ant trails and then apply a perimeter treatment if desired for additional protection.
ANT BAITS. Ant baits are valuable tools and can be used in most every ant infestation, but should not, in most cases, be relied upon as the sole treatment strategy — except for Pharaoh ants. Follow the steps described previously to find and treat as many colonies and active ant trails as possible, then use baits to supplement those other efforts.
Where the colony cannot be found or where large numbers of ants are present, baits can play a significant role in resolving the situation.
When baits are used, placing several different types/forms of ant bait will determine which the target ants prefer (see photo below). More of the preferred bait should then be placed along trails. It is also advisable after placing ant baits to revisit later (hours or next day) to see if the target ants continue to feed on the bait. Sometimes, ants actively feed on a bait then abandon it, often within 10 to 20 minutes after it is placed.
The more the situation must rely on baits, the greater the need for frequent follow-up visits to determine if more of different ant baits are needed.
LIQUID BAIT STATIONS. For severe ant situations with high ant pressure (e.g., Argentine ant, tawny crazy ant, white-footed ant), liquid ant bait stations placed at the perimeter of the property, where ants are active and at the base of trees or shrubs where foraging ants are accessing aphids and other honeydew-producing insects, can give these ants an alternative food resource that reduces numbers. In addition, liquid bait stations can draw ants from inside structures by giving them a more preferable food source outside. Liquid stations, however, require more frequent follow-up, such as weekly, to refill stations or to add or move stations as necessary. Even when using liquid bait stations, efforts to find and treat ant colonies and trails is important.