From where are they coming?

There’s another one and another one! Ants, yes those pesky ants, inside the home. Even though there are dozens of different ant species that may be found in the home, the most common household-invading ants include pavement ants, carpenter ants, acrobat ants, and odorous house ants. Management techniques for each one are based on the specific species’ characteristics.

The common mistake when attempting to control ants is only spraying the ones present. The ants seen foraging over exposed surfaces are only a small portion of the colony. Typically, there will be thousands of additional ants, including one or more egg-laying queen, hidden somewhere in a nest. The importance of eliminating queens and other colony members within nests cannot be overstated and is key to effective ant control.

Ants build their nests in many different locations, both inside and outside buildings. Species nesting inside, or foraging indoors for food or moisture, tend to be the most challenging to control.

Preferred nesting sites for ants include spaces behind walls, cabinets, appliances, or window and door frames, or beneath floors and concrete slabs. These hidden areas can make it difficult to determine their precise location.

When the nest’s location cannot be determined or is inaccessible, insecticide baits are the preferred solution. The advantage of using baits is that foraging ants take the insecticide back to the nest and feed it to the queen or queens and other members of the colony. If all goes well, the colony is destroyed.

When using baits, place them wherever ants are seen, preferably beside ant “trails,” invisible odor trails worker ants follow between food and the nest. Do not spray other insecticides or cleaning agents around the baited locations as this keeps ants from eating the bait. Initially, the number of ants around the bait station will increase.

This indicates that the ants are feeding on the bait and transporting it back to the nest. Ant activity will hopefully subside in a few days as the number of ants in the colony declines. Continue to place other baits wherever ants are seen.

Ants are rather finicky in their food preferences and may alter them throughout the year. If one bait isn’t attractive, try another. Optimal results usually require a sustained period of feeding, not just a brief visitation by a few ants. Retail baits usually will not control carpenter ants.

The odorous house ant has become the most common and difficult to control. This ant is small, darkish in color, and forms distinct trails along floors, countertops, sidewalks, foundation walls, etc.

The odorous house ant is often mistaken for the pavement ant, which can easily be controlled with most baits. The most accurate diagnostic difference is the absence of a noticeable “bump” or node along the constricted area between the thorax and abdomen.

Pavement ants have two obvious nodes and fine grooves or striations along the head and thorax. A good quality hand lens, or ideally a microscope, is needed to see these characteristics.

In addition, pavement ants are more likely to “kick out” bits of dirt or debris from their typical nesting location under slabs or along walls. Odorous house ants, in turn, give off a rotten coconut or pine-like scent when crushed.

Odorous house ant colonies can number in the tens of thousands with multiple nesting sites in just about every imaginable location. The ants commonly nest outdoors under pavement, rocks, mulch, woodpiles, flower pots, and siding and forage indoors for food and moisture.

Nests may also occur behind brick veneer or indoors within wall voids, potted plants, appliances, and especially near sources of moisture. Odorous house ant nests tend to be mobile. The colonies relocate fast, often in response to changes in weather, disturbance, and other factors.

Colonies usually have multiple egg-laying queens and may split into smaller colonies. Ants foraging indoors feed on all manner of foods, ranging from the trash can to the cereal bowl, but generally prefer sweets.

This particular ant is very difficult to control, especially by householders. The better baits to try are often sweet ones. Activity indoors can sometimes be alleviated by eliminating ready food sources such as spillage or pet food dishes.

Sealing obvious ant entry points may also be helpful, along with trimming back shrubs and limbs that serve as ‘bridges’ to the building. In nature, this ant feeds extensively on plant nectar and honeydew excreted by plant-sucking insects such as aphids.

Help is often required to know which ant or ants you have. Ants placed in a container with white vinegar can be brought to your local Cooperative Extension Office for identification, free of charge through the University of Kentucky’s Entomology Department. During the pandemic, calling or emailing before leaving a sample outside the building is preferred.

For more information, contact the Daviess County Cooperative Extension Service at 270-685-8480 and leave a message or by email at daviess.ext@uky.edu. The publication “Ant Control for Homeowners” (http://entomology.ca.uky.edu/ef619) contains information about baits and other management options.

Annette’s Tips:

Identifying ants is the first step in management. When trying to control odorous house ants, you may need to call a professional. You may also need assistance when dealing with carpenter ants. It may be more challenging to find an active nest. A publication about carpenter ants is available at the website https://entomology.ca.uky.edu/ef603.

The University of Kentucky Cooperative Extension Service’s weekly newsletter called “Healthy at Home: Navigating COVID-19 with Cooperative Extension” is available at https://extension.ca.uky.edu/healthy-home-newsletter.

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