The Homeowners Column

The Homeowners Column

Household Ants and their Control

Photo of Sandra Mason

Sandra Mason
State Master Gardener Coordinator
slmason@illinois.edu

Last year the ants paraded into our homes looking for water. This year I think they must be searching for high ground. I'm pretty sure the ants marching across my counter are wearing floaties.

Outdoors in lawn areas ants rarely need control. Ants are important in aerating the soil, controlling pests as they forage for insect eggs and even in dispersing seeds of many wildflowers.

Most indoor ants are primarily an ongoing nuisance and cause little damage. Generally no disease problems are associated with ants. However carpenter ants can weaken wood in structures with their nests often near roof, windowsill or drainpipe leaks. However unlike termites, carpenter ants do not eat wood.

How do you tell the difference between a winged ant and a winged termite? Several attributes will lead to the correct identification. Ants have bent antennae (imagine an arm with a bent elbow) and termites have slightly curved, beadlike antennae (imagine a string of pearls). Ants also have a narrow constricted waist while termites have a broad waist. Ants have two pairs of wings that are unlike in size and shape while termite's two pairs of wings are similar in size and shape.

Ants have a wide range of nesting habits and food preferences. Proper identification is important in determining control measures. Some ants build nests in soil with their characteristic mounds while others nest in homes behind moldings, baseboards, countertops and similar places. Ants feed on a variety of foods including starches, meats, fats and sweets.

A common indoor ant is the odorous house ant. It gets its name from the unpleasant smell it releases when it's crushed. Odorous house ants are brown to dark brown. They are particularly small with the workers about one tenth of an inch long. They like to eat sweets and fatty foods. No wonder they like hanging with us. They nest in soil under stones, boards, patio blocks and nearly any other object lying on the ground. They can nest in homes in wall voids, under floors and even in potted plants. Odorous house ants do not cause structural damage to buildings.

Spraying a pesticide indoors on the occasional worker ant foraging for food is only temporary and has little if any impact on the nest. A quick spray of soapy water can be used to eliminate the wandering foragers. The nest should be found and treated for long-term ant control.

Sometimes the nest becomes obvious by following the ants. Ants usually take regular routes to and from their nest and their food by establishing a chemical scent trail. Instead of leaving breadcrumbs to find their way back, they leave a smell to find their way back to the breadcrumbs.

First step in ant control is good sanitation, which means no dirty dishes in the sink and wiping counters regularly. Caulk cracks and crevices in house foundation. Keep foods in tightly sealed containers.

Commercial baits can be effective on some ant species. However in order for the baits to work, there must not be any other food sources available. Do not set baits where small children or pets can reach them. When using any pesticide be sure to read and follow all label directions.

To control odorous house ants check for outdoor nests especially under stones, firewood or bricks. Move wood chips at least a foot away from the foundation of the home. Check indoors in the potted plant you rarely water.

If nests are not located, your best bet for long-term control is to call a local professional pest control company. Professionals may be more experienced at finding the ant nest.

Join us in Danville, Onarga or Champaign for the UI Extension Telenet – "Pollinators and Insecticides" on April 23 at 1 p.m. For more information http://web.extension.illinois.edu/cfiv/ or 217-333-7672.

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