By Yvonne Rasmussen, U. C. Master Gardner

At this time of year, I start to notice the ants in my garden, and sometimes in my house. In the garden I see them mostly when I water in an area that has been dry for awhile. They come boiling out from various places, frantically carrying their eggs and young out of the ground to keep them from drowning.

In the garden, ants are rarely a problem, but they can be an indication of other insect problems and sometimes a nuisance. I rarely see ants inside the house, but when I do, I know they must be going to a source of water or food.

I follow the trail until I find where they are going. If it is a food source, I clean it up, and within a day they are gone. If they are seeking water, not food, then it may be a bit more work to isolate the source and eliminate the ants. Next step is to finding where they are getting in and caulking or sealing the entryway.

There are more than 12,000 species of ants in the world and about 200 species in California, but the good news is that only about a dozen are considered important pests. The most common ant we see in our garden and home is the Argentine ant. These are small grayish-black to brown ants traveling in long trails to and from their food source.

They are attracted to sweet food sources most of the year—to protein in the spring—and they nest in shallow spots underground. By late summer, they can build up large colonies that may be connected and have multiple queens.

In Napa Valley, we also have pharaoh ants, house ants, thief ants, Southern fire ants, velvet tree ants, and carpenter ants. These different types can be identified by their size and color. Luckily we do not have the red imported fire ant that has been found in  Southern California. It is an aggressive stinging and biting ant.

If ants are causing you problems and you want to control them, management starts with proper identification. Once you know the type of ant and its behavior, you can plot effective control. Catch a few and throw them in the freezer to slow them down. For a good ant identification key, plus tips on control, visit the University of California Integrated Pest Management website (www.ipm.ucdavis.edu) or the Napa County Master Gardener help desk (see address below).

Do you really need to control ants in your garden? In the yard or garden, ants can be beneficial because they eat dead insects, animals and fallen fruit. They can also be useful for seed dispersal and soil aeration.

Sometimes ants will eat fruits and nuts, but most often they are a problem when they are tending pests such as soft scale, mealy bugs and aphids. These pest insects feed on plant sap and excrete a sugary substance called honeydew. This honeydew attracts ants; they will feed on it and protect the pests from predators. The ants will move the pests to new areas of the plant, thus spreading the trouble. A trail of ants up a trunk is often the first sign of a pest infestation.

By controlling the ants, we can often control the pest. On single-trunked plants, apply a sticky material such as Tanglefoot and trim branches so they don’t touch the ground, other plants or structures. Check the sticky substance regularly to make sure it is not clogged with dirt, debris or dead ants.

Bait stations are most effective in late winter and early spring when populations are small. Try using a variety of baits since they all have different attractants. For more information on controlling ants, visit http://cenapa.ucdavis.edu.