House Ant Control

- How to safely control ant pests -

Summary: Certain ants commonly invade homes looking for food and water. These ants are generally small and can be a nuisance but cause little other damage. Use sanitation and insecticidal baits to keep them under control. Don't use aerosol ("spray can") insecticides because they can cause the infestation to spread to other areas.

Jack DeAngelis, PhD

OSU Ext. Entomologist (ret.)

my resume

House-infesting nuisance ants

There are a few different species of small brown ants that invade homes looking for food and water. These so-called house-infesting ants include odorous house ants, Argentine ants, pharaoh ants, and a few others. Small ants like these are difficult for homeowners to tell apart but fortunately exact identification is not necessary for effective control. And, none of these ants cause significant damage nor do they pose any health risk.

All ants live in colonies that are dominated by an egg-laying queen. Worker ants (all females) forage outside the colony for food, they also expand and defend the nest. Ants feed on a wide variety of foods including carbohydrates (sugars), proteins, fats and oils. Colonies, or "nests", are usually located in protected places in walls, under floors, under cabinets, and individual colonies can be quite large with thousands of worker ants

House ant control

Your first step should always be sanitation. Clean up crumbs, cooking oil, and all sources of water. This alone will go a long way toward reducing ant problems by depriving foraging ants of food and water. Also, patch holes around pipes and wires that pass into the living space. Ants use these "highways" to gain entry from colonies located in walls, the crawlspace, and so forth.

Next, use ant bait to suppress or eliminate colonies. Do not use conventional aerosol insecticides as these can be messy and ineffective. Insecticidal sprays can actually make matters worse by causing colonies to disperse and by blocking access to bait placements.

Effective ant baits are available commercially (see below) as liquids, gels and granules. Liquid baits can even be homemade (see Using Homemade Ant Baits). Place liquid and gel baits near ant activity and trails, granular baits can be used outside around the perimeter of structures and in similar places.

Baits work better than sprays

Baits work much better than conventional insecticides because of the unique way worker ants feed their colony, including the queen. When a foraging worker locates food she returns to the colony and recruits other workers to the food source. The recruited workers collect food (see photo above) in a special pouch called a crop and return to the colony where they feed other ants, a process called "trophallaxis". Because of this the most effective baits are slow acting, giving the worker enough time to get back to the nest and pass the poisoned bait to other colony members, and eventually the queen. Conventional insecticides disrupt this behavior and can render baits ineffective.

Many small infestations can be controlled with inexpensive liquid baits that are available commercially and can even be homemade. Larger, difficult-to-control infestations should be treated with granular baits on the outside and gel baits inside homes. Granular baits can be used to treat large outdoor areas such as the perimeter of a building. Gel baits can be used indoors as spot treatments. See the package instructions that come with each product for use details.

Every situation will be a little different but if you notice ants outside that seem to be moving toward the house then treating the outside perimeter with a granular bait such as Advance Granular or Maxforce Granular may be needed. These baits can also be used for general ant control outdoors. If you've tried liquid bait indoors and still have a problem then gel baits like Maxforce Gel, Advion Gel or Optigard Gel may be the answer. Each gel has a different active ingredient and food component so a little experimentation on your part may be needed.

Control of Common Nuisance House Ants With Baits

(1) Place baits near ant activity, do not contaminate area with insecticide. You can initially place a plain, sugary bait (no insecticide) to train workers to the placement. If ants appear to be feeding on bait, as in photo above, replace plain bait with one laced with insecticide. For small infestations use ready-made, or home-made, liquid boric acid baits. But, for large, stubborn infestations use commercial gel or granular baits, both are available here (DoMyOwn.com).

(2) Replace individual stations when they are exhausted or completely consumed.

(3) Within a week the number of ants should be significantly reduced.

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