School IPM Best Practices

Odorous House Ant, Tapinoma sessile

Odorous house ant

Joseph Berger, Bugwood.org.

IPM Steps to reduce Odorous House Ants

1. Sample for Pest

Before taking any action, confirm the presence of more than one ant—it may have come in on clothing or packaging. Inspect the adjacent areas along walls (interior and exterior) now and again later. An ant or two may be searching for a food source—don’t let them find it! Develop a knowledge of where ants are likely entering and make a practice to inspect and anticipate.

Where to find it while inspecting: Search for activity of more than one ant. Multiple workers (without wings) suggest a nearby, outdoor nest. Winged ants inside suggest a nest inside. If crushed, this ant can be identified by the foul odor which gives it another common name “stink ant”.

2. Proper ID

To best treat a pest, you must be sure what it is.

Size and Particulars: 1/16"–1/8" (24–33 mm) brown to black.

3. Learn the Pest Biology

Ants follow scent trails to and from food sources.

Life Cycle: Winged adults mate in spring through mid-July and form new colonies.

Preferred Food Sources: Feed on dead and living insects plus honeydew (aphid and scale feces), they forage homes for any food source, preferably sweets. You may see them following scent trails to indoor food sources.

Preferred Habitat: Live in shallow nests under debris, wood and small stones, widely adaptable to greater habitat, will nest in wall voids and around sources of heat and moisture. Colonies can grow quite large. Odorous house ants are very tolerant of extremes in heat, cold and moisture.

4. Determine Threshold

If you’ve seen ant activity inside, you need to act.

Threshold: They can be difficult to control so any sighting of ant activity means you must act.

5. Choose Tactics

IPM for indoor pests is always a combination of exclusion and sanitation: Don’t provide access to water, food and shelter!

Best Management Practices: Keep all cracks and gaps in foundations, walls, windows and vents sealed. Keep plant and mulch debris away from foundation. Reduce moisture prone areas inside. The number one way to prevent ant problems inside it to block access to food sources

Treatment Methods: If a nest is found inside, it must be removed. Call a professional or remove it by vacuuming with an industrial vacuum, (vacuum up some corn starch as well) and then destroy the vacuumed material. This will reduce but will probably not destroy all ants as a nest will contain a few dozen to a few thousand ants, and not all will be in the nest at the time. Low-toxicity methods: (do not use if you are also using a bait) Place near the nest: diatomaceous earth, a desiccant which dries out the insect bodies; pyrethrum products, a chrysanthemum derivative; silica, another desiccant sometime sold in combination with pyrethrum; commercial products containing boric acid, an effective poison for insects with low toxicity to humans but must be used with extreme caution and may not be suitable or legal in your district. Cut back branches and plant material that touches buildings. ALWAYS READ THE LABEL FOR ANY PRODUCT’S SPECIFIC DIRECTIONS.

Insecticide options: Insecticide options: Bait traps contain insecticide introduced in a food source. ODOROUS HOUSE ANTS will only respond to baits considered “sweet”. Due to the nature of the bait trap and the amount of insecticide, they are generally considered safe for use in schools and homes. Keep out of reach of children. For a bait to be effective you must: 1) reduce any other access to a food source—sanitation and exclusion by keeping all foods in airtight containers. 2) do not kill ants as they must carry the food (bait) back to the colony where it will be a deadly food source for the colony. You may see an increase in ants at first but then a slow decline. Do not spray insecticides at this time. Be patient. At times, a perimeter treatment may be used, but this must not be a non-repellant product.

6. Evaluate

Was the tactic successful? Record the date pests were first noted, and the tactic you used, and its success. Use one of our RECORD KEEPING tools

For More Information:

UC IPM Online: Odorous House Ants

UC IPM Online: Odorous House Ants: Quick Management Tips

Iowa State University: Odorous House Ants

Cornell’s Insect Diagnostic Lab: Ants in Houses (PDF)


When a pesticide application is necessary, all necessary and required precautions are taken to minimize risk to people and the environment and to minimize risk of pesticide resistance or pest resurgence. Pesticide use in your school may be prohibited or regulated by local policies or state and federal regulations. Risk reduction methods can include, but are not limited to, spot-treatment, the use of gel or paste bait formulations placed in inaccessible locations, injection into a crack or crevice, and other methods that reduce potential exposure.