Q For about a month we have had small brown ants appearing in different places in the house. They were appearing before the snow was gone. We used ant spray on the baseboards and put out ant traps, but nothing seems to reduce the frequency with which they appear. What can I do to eliminate them?

A Seeing ants during cold months suggests that you have a nest in your home. How you treat these ants depends on which species is present and where they are nesting; there isn't one method that will control all ants.

However, it is safe to say that spraying baseboards will not control an ant nest. Just a small number of ants from the nest are out foraging at any one time, and it is much too difficult to kill the nest through attrition.

One possible candidate for your problem is the pavement ant. They fit your general description and they like to nest in the soil underneath objects, such as stones, bricks, sidewalks, driveways and wood. They are also common in homes, nesting under concrete slab construction, and can be found indoors throughout the winter. They are also known to nest in small voids in homes.

The best way to eliminate pavement ants that are nesting under concrete slab construction is to bait them when sealing any expansion joints or other cracks where the ants are coming up through the concrete. An advantage to baiting is the worker ants carry the insecticide back to the nest and as long as they take enough bait back to the nest, they can eliminate the queen and the rest of the nest. A disadvantage is that it can take a long time, even weeks, to be effective.

Also keep in mind that you should never spray insecticides while using bait, as any spray will kill ants before they can transport bait back to the nest. It isn't unusual to see pavement ants indoors during the winter but not during spring and summer as they forage outdoors for food.

Other ant candidates

You could be seeing other ants, including Pharaoh ants, odorous house ants, cornfield ants or even carpenter ants (yes, there is a small species that is reddish-brown and black). You would treat each of these ants differently.

Your first step in controlling them is to correctly identify them. Your local county extension office or a pest management company could help you identify them and suggest a treatment option. Keep in mind that some ants are best controlled by pest management professionals.

Jeff Hahn, entomologist, University of Minnesota Extension

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