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Caption: Odorous house ant

Photo by: Susan Ellis, Bugwood.org

Odorous house ants

(revision date: 6/26/2023)

Use Integrated Pest Management (IPM) for successful pest management.

Biology

Odorous house ants are extremely small. Workers are approximately 1/16 inch long and have a uniform brown to black color. They nest in the soil in shapeless, shallow, and temporary colonies, as these ants frequently move. They feed on a wide variety of things including nectar, honeydew from aphids, and living and dead insects. They easily enter homes where they feed on dairy products, fruit juices and pastry. They are perhaps the most difficult ants in our area to discourage. Swarming occurs throughout the year but most commonly in June and July.

Management Options

Non-Chemical Management

Prevention of conditions conducive to invasion is the only non-chemical option as these ants send scouts into areas of potential food presence. If kitchens are kept as clean of food and liquid residues as possible, it will help to discourage them from returning.
Using a sponge and soapy water, wipe-up any ants and their trails that you see.
Seal all potential entry points. This can be extremely difficult since the ants are small.
Keep trees and shrubs from touching buildings.
Keep odorous house ants off landscape plants near buildings.

Select non-chemical management options as your first choice!

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

Try to find the nest if possible. Odorous house ants follow trails which are visible after noon, but not necessarily at night. You can use a flashlight to follow the ants using trails from their nest to your home. If detected, treat the nest. If the nest cannot be found, treat the area where the foundation and soil meet to form a chemical barrier. There are also bait materials you can use indoors.

If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.

Combat MAX Ant Killing Gel
Active ingredient: fipronil | EPA reg no: 64240-42
Combat Outdoor Ant Killing Granules
Active ingredient: hydramethylnon | EPA reg no: 64240-25
Amdro Kills Ants Ant Killing Bait
Active ingredient: hydramethylnon | EPA reg no: 1663-33-73342
Bonide Termite & Carpenter Ant Killer Conc
Active ingredient: permethrin | EPA reg no: 4-349
Terro Ant Killer II Liquid Ant Baits
Active ingredient: sodium tetraborate decahydrate | EPA reg no: 149-8
Raid Max Double Control Ant Baits
Active ingredient: Avermectin B1 | EPA reg no: 4822-472
Orthro Bug B Gon Insect Killer/Lawns and Gardens R-T-Spray
Active ingredient: Bifenthrin, Zeta-cypermethrin | EPA reg no: 279-9535-239
This list may not include all products registered for this use.

Images

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Caption: Odorous house ant Photo by: Susan Ellis, Bugwood.org

WSU Extension

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