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Growing Green: Bugged by Ants

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I have received many calls recently requesting information about how to get rid of ants in the home and lawn. Ants are the most frequent and persistent pests encountered around homes and buildings, and they have been a particular nuisance this year. Dealing with ants can be very frustrating. The first step in implementing an ant management program in your home is to learn what type of ant you are trying to remove. Ants have a wide variety of nesting habits and food preferences. Knowing what species of ant is present helps to determine the nesting site, food preference, and the best method of management.

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The common household ants found in Minnesota are:

Carpenter Ants: Black, or red and black; workers range in size from 3/16 to 1/2 inch. Eat meats and sweets. (They do not eat wood!) May nest in rotting wood, behind bathroom tiles, around tubs and showers, in attic beams and under subflooring. Management: apply pesticide directly to nest.

Cornfield Ants: Light to dark brown; workers are about 1/10 inch long. Eat sweets. Usually nest in soil, forming small mounds in lawns. They rarely nest in homes. Management: treat nests in the lawn and other nearby areas. If nests are not obvious, treat the building perimeter with a residual spray.

Larger Yellow Ants: Yellowish to reddish brown; workers are about 3/16 inch long. Eat honeydew (a sweet substance created by aphids and scale insects.) May nest in soil, in and around foundation walls and under stones, logs or other protected areas. Rarely seen in homes except during mating swarms. Management: physically remove winged ants with a vacuum. For large swarms, apply an insecticide labeled for flying insects.

Pharaoh Ants: Light yellow to red with their thorax darker colored; workers are about 1/16 inch long. They prefer grease and fats, but will feed on sweets, dead insects, toothpaste, and soaps. These tiny ants can nest in very small spaces, and always nest indoors. Their nests are difficult to find due to their size. Management is difficult. Baits are recommended for home use. In extreme cases, call a professional pest management service.

Thief Ants: Yellow to light brown; workers measure about 1/20 inch long. Prefer greasy foods like meat, cheese, peanut butter and nuts, but will eat sweets if available. Outside, nests in soil and rotting wood. Inside, nests in small spaces under countertops, behind walls and cabinets. Management: nests are difficult to find. Treat the building perimeter with a residual spray, and use baits indoors.

Pavement Ants: Reddish brown to black; workers are about 1/8 inch long. Eat a variety of foods, meat, sweets, dead insects, pet food, bread and nuts. Nests in soil, foundation cracks, under logs or stones, and other concealed spaces. Management: treat the building perimeter with a residual spray and use baits specific to grease feeding ants indoors.

Most people only spray the ants they see, not realizing that this is just a small portion of the existing colony. A colony typically includes thousands of additional ants including one or more egg-laying queens. To be effective, any control method should focus on eliminating queens and other colony members within nests. When the location of the nest is inaccessible or can't be found, insecticide baits are a good option. These baits attract foraging ants which then take the insecticide back to the nest and feed it to the queen and other colony members, effectively destroying the entire colony. Most baits sold to homeowners come pre-packaged with the insecticide and food attractant confined within a plastic, child-resistant container.

Common pesticides for treating lawns and around buildings include: permethrin, carbaryl, bifenthrin, cyfluthrin, acephate and daltamethrin. Be sure to select a product labeled for lawns or building perimeters. Use exactly as labeled.

For more information about common household ants, visit the University of Minnesota Extension website at www.extension.umn.edu.

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"It is not enough to be industrious; so are the ants. What are you industrious about?" ~ Henry David Thoreau

Robin Trott is a Horticulture Educator with University of Minnesota Extension.

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