The Homeowners Column

The Homeowners Column

Household Ants and Their Control

Photo of Sandra Mason

Sandra Mason
Extension Educator, Horticulture
slmason@illinois.edu

The first thing you notice is a crumb from your midnight cherry pie raid has sprouted legs and is moving across the kitchen counter. What was last night's cast off is now a feast for a family of ants. I have had so many questions about ants recently, I knew it was time to repeat some ant information. Ants can be common pests in homes. Damage from ants varies. Most ants are primarily a nuisance and cause little damage. Carpenter ants can weaken wood in structures. However unlike termites, ants nest in wood but do not eat wood. Generally there are no disease problems associated with ants.

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 producing characteristic mounds while others nest in homes behind moldings, baseboards, countertops and similar places. Still others like carpenter ants nest in decaying or moisture damaged wood. Ants feed on a variety of foods including starches, meats, fats and sweets.

That's why they hang out in the kitchen with us. Not all ants found outdoors become pests. Ants are important in aerating the soil and even in seed dispersal of many wildflowers. Some ants have even been known to eat lawn grub eggs. Ant colonies in lawn areas generally do not require control.

A common ant is the odorous house ant. It gets its name from the unpleasant smell it emits 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 other foods including meat. 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 on the occasional ant foraging for food is only temporary and has little impact on the nest. However spraying may be useful for seasonal ant problems when ants enter from outside nests. Indoor sprays include chemicals such as diazinon or permethrin. Be sure a pesticide is labeled for indoor use and read, understand and follow all label directions.

The nest should be found and treated for long term ant control. To find the nest, follow the ants. Ants usually take regular routes to and from their nest and their food by establishing a chemical scent trail. Instead of leaving bread crumbs to find their way back, they leave a smell to find their way back to the bread crumbs.

To control odorous house ants, check for outdoor nests especially under stones, firewood or bricks. If nests are not located, ants can be kept out of the house by applying an insecticide barrier around the outside of the home. Areas that attract ants on a regular basis can be spot treated. If it is not clear where the ants are entering, then treat a 2-4 feet wide area around the entire building. This control method is temporary and re-treatments may be necessary. Outside pesticide sprays include diazinon or chlorpyrifos sold as Dursban. There is no scientific evidence that spearmint gum, red pepper, orange peels or various herbs repel ants effectively.

Commercial baits can be effective. Do not set baits where small children or pets can reach them. A mixture of boric acid and honey or syrup is also attractive bait.

For more information on identifying ants and their proper control measures, contact the Universtiy of Illinois Extension in Champaign County at 801 North Country Fair Drive, Champaign 217-333-7672 for the brochure entitled What to Do about Household Ants.

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