Resident must find, kill carpenter ants

I see these big black ants inhabiting a tree in my yard. What kind of ants are they and what can I do to kill them?

A: These big black ants are carpenter ants. Because I occasionally get some calls about them, I will explain a little about the biology of them so that you and others will understand the steps to take to get rid of them.

Carpenter ants get their name from their habit of chewing wood to create nest sites. They do not eat wood, like termites, but excavate it with their strong, serrated jaws to create random galleries where they nest. Carpenter ants are also a nuisance because of their abundance and size.

Carpenter ants are the largest of the pest ants found in Georgia and South Carolina. They are most active at night when it is not uncommon to see twentyfold or more ants than would be seen during the daylight hours.

Ants emerge about 15 minutes after sundown and leave the nest in large numbers in search of food, traveling up to hundreds of feet from the nest on semipermanent trails. In the evening, ants can be seen using these trails as they emerge from and return to their nest. Colonies may even use the same trail in different years.

Carpenter ants may establish nest sites inside and/or outside the home. Some examples of places where carpenter ants have been found nesting inside are moisture-damaged wood, around chimneys and skylights, under bathtubs, inside dishwashers, in wall voids beneath window sills, inside hollow doors and door frames, under fiberglass insulation in crawl spaces, in wood porch supports and columns, under siding and wood shingles and in moisture-damaged eves.

In general, wood suffering from moisture damage will attract and be used by carpenter ants as nest sites because damp wood is easier to chew than sound, dry wood. Damp wood, combined with warm temperatures, also promotes the survival, growth and reproduction of carpenter ant colonies.

Outside, nests are most commonly found in hardwood trees containing holes. In tree holes, ants find an environment that is ecologically stable (consistent humidity and temperature) and protected from adverse, environmental conditions and natural enemies.

The key to eliminating carpenter ant infestations is to find the nest and remove it, either physically (by a vacuum) or by treating it with an insecticide. Inspect all locations I listed above for indoor and outdoor nest sites.

To find a nest site indoors, follow a few foraging ants to learn where they might be nesting. Tap the suspected area. This excites the ants allowing you to detect their presence by hearing their raucous movement.

Look for small piles of wood debris, resembling sawdust, that ants drop from the nest during excavation of the wood. Close examination of the debris may also reveal parts of dead carpenter ants and the uneaten, discarded pieces and parts of prey insects brought to the nest for food.

Carpenter ants found in the home often times can be found nesting outdoors in trees. To find outdoor nest sites inspect each large tree (greater than 6 inches in diameter) beginning 15 to 20 minutes after sundown by walking around it while shining the flashlight up and down the trunk. If a nest is present, ants will be seen moving up and down the trunk as they leave from and return to the nest with food.

Since carpenter ants use permanent trails, use a flashlight to find ants on the trail and then follow them as they move to and from their nest. Finding part of the trail can be a tremendous help in finding the nest. After locating several points along a trail, a directional pattern will emerge and often lead directly to the nest.

Since carpenter ants must excavate wood to expand their galleries, it is common to find piles of sawdust on the ground at the base of a tree where they nest. Galleries are created by biting off small pieces of wood and disposing of it to the outside.

Any insecticide you use will be effective in killing carpenter ants. The key is getting it to the nest.

Sid Mullis is Director for the University of Georgia Extension Service Office in Richmond County. Call 821-2349, or send e-mail to smullis@uga.edu.