Prevent or control a nest of carpenter ants

By Joan Allen - UConn Home & Garden Education Center
Featured Article - posted Thu., May. 10, 2012
- Contributed Photo

After a winter of little activity, carpenter ants foraging for food will start to reappear inside the home. During late winter and early spring, ants nesting within structures are most active from late evening to early morning. Daytime activity will increase through the spring and into summer.

How do you know if you have carpenter ants? Three species of carpenter ant invade homes in Connecticut. The most common is the black carpenter ant, Camponotus pennsylvanicus. Adult workers and reproductives are black and have a narrow wasp-like waist. This is in contrast to termites which have wide waists. Termites are also light-colored and are rarely seen outside of their colonies. The black carpenter ant is one of the largest ants in New England.  Workers are ¼ to ½ inch in length and winged reproductives, called swarmers, are ½ to ¾ inch long. Ant swarmers have brown wings, with the front pair longer than the rear pair. In termites, all the wings are the same size.

A carpenter ant colony consists of a queen and workers. The queen lays the eggs and the workers’ duties include caring for the eggs, larvae and pupae, foraging for food, and excavating and protecting the nest. A colony matures in three to six or more years to a population of about 2,000 ants. At this point, winged males and females are formed and they leave the nest in the process known as swarming. This can occur as early as January for colonies in heated buildings. Outdoors, swarming and mating occur from late spring to mid-summer. Males die shortly after mating. One in a thousand of the fertilized queens will be successful in establishing a new nest.

The newly-fertilized queen begins a nest by finding or excavating a small cavity, usually in moist or decayed wood, and lays 15 to 20 eggs. She cares for these young workers and they then take over all the duties of the nest while the queen continues laying eggs.

Outdoor nests are usually in decayed cavities of trees, fence posts and stumps. Workers will forage for food 65 feet to 100 yards from their nest. They feed primarily on honeydew, a predigested sap excreted by aphids and scale insects. Other foods include insects and small invertebrates.

Indoor nests are most common when a building is located near an outdoor nest. Nests are found in firewood, hollow-core doors, ceilings, attics and behind window frames and sills. They are commonly found in areas of the structure that trap moisture, such as where a porch, garage or deck attach to the building.  Nests also occur in bathrooms in tile-covered walls surrounding bathtubs, and flooring surrounding tubs and toilets.

Carpenter ants forage both inside and outside for food. Foraging activity is often in the kitchen, under sinks, dishwashers and refrigerators. They prefer sweets such as jam, sugar and overripe fruits. Crumbs, grease and fats are also attractive.

Control of carpenter ants in the home can be easy or difficult, depending on circumstances. Control will be more effective if you can locate the primary nest site. Conduct your inspections when ants are most active, generally late evening in spring and early summer.

Look for sawdust that worker ants leave outside their galleries. Watch ant traffic and follow them to the nest. Nocturnal noise in walls or voids indicate nesting activity.

The two control methods are structural and chemical. Structural control consists of eliminating potential nesting sites by eliminating moisture problems. Replace rotted wood, leaky gutters and damaged roof shingles, etc. Grade the ground to prevent wood on garages, decks and porches from contacting the soil. Provide adequate ventilation to areas such as crawl spaces and attics.

Chemical controls include baits and sprays. Baits are a mixture of an attractive food and a pesticide. The workers carry this food back to the nest and feed it to the queen and other ants. There are several commercially available bait products. Ant activity should decrease in about a week, but it may take several weeks to achieve control. Sprays are most effective when used directly on ants in their nest. Several formulations are available for home use. Before using a pesticide, be sure to read and follow all label instructions and precautions.

If you have questions about carpenter ants or any other home or gardening topic, call, toll-free, 877-486-6271, visit the website or contact your local Cooperative Extension Center.


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