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Recycle A to Z

alternatives to pesticides - bugs/pests - Carpenter ants

                           carpenter ant
                                  Actual size: 1/4” – 1”

Unlike termites, carpenter ants don’t actually eat wood. They nest in it. If you find them in your house, look for a good professional who understands your concerns about toxic chemicals and will work with you to select a least-toxic control program. While they can cause serious damage to houses, these ants are actually beneficial insects in the forest, where their excavations help speed the decomposition of dead trees. In fact, they prefer to build their nests in decayed or rotted wood, but will eventually extend their tunneling into sound wood if they can’t find decayed wood.

Positive identification requires collecting a few of the largest ants and inspecting them under a magnifying glass. Carpenter ants have a smooth upper back, while most other ants have a dip in this area. Suspicious signs include sawdust and debris, rustling sounds in the walls and trails of ants between the foundation and wood outside the home.  Carpenter ants eat dead insects, honeydew exuded from aphids, plant juices and sweet or fatty foods in the home.

To assess the extent of the problem, locate the main colony. Seventy-five percent of all main nests are located outside the house where there is abundant moisture, such as in an old tree or tree stump above or below the soil surface. Satellite nests may be found inside your house, in walls and ceilings, under outdoor siding, near downspouts or roof gutters, in floors – particularly bathrooms – or in insulation. Begin with the basement and work up to the attic, looking for the ants and sawdust-like wood shavings.


Prevent moist wood through adequate home mainte­nance. Repair any rotten or weather-damaged wood and make sure that attic and crawl space ventilation is adequate. Place plastic sheeting on ground surface of crawl spaces as a vapor bar­rier and improve ventilation to damp areas.

Inspect gutters and downspouts to be sure they do not leak and that water is being diverted away from the house. Clean out the gutters. Remove potential sources of ant nests and other means of access which are close to the home: trees and shrubs should be pruned back so that they do not touch the house or garage, including roofs.

Stumps should be completely removed. Even decorative bark may harbor carpenter ants and provide nesting sites. Check firewood carefully for insects before bringing it inside. Firewood should not be piled against the side of the house. It should be elevated off the ground and kept away from the house.

Physical Control

Locate and remove all nests, capture stray ants, caulk access points and replace all damaged wood. This sounds like a tall order, but if the infestation is accessible and has not spread too far, you can be successful.

Least Toxic Chemical Controls

Use desiccating dusts, such as:

Diatomaceous earth or silica gel. Diatomaceous earth is made from ground up fossils; it comes in a powder form and is very abrasive. It is a dust that abrades the skin and body joints of insects. Dry diatomaceous earth makes an effective slug barrier. Do not inhale the dust.

Boric acid can be blown into wall voids. Boric acid is a slow acting, low-toxicity, long-lasting (if kept dry) powder that is effective against ants, cockroaches and other structural pests. It is a digestive and contact poison and is usually applied as a dust. Products often come with a duster-type applicator. It is toxic if ingested, inhaled or comes into contact with abraded or broken skin. It poses a risk to children and pets if they come into contact with it. It is safe to place it in wall voids because it does not evaporate and cannot enter living spaces.

Pyrethrum - Pyrethrum is an effective, short-lived, naturally derived insecticide made from chrysanthemum flowers. It is toxic to all insects, including beneficial ones, and moderately toxic to birds and mammals. It should be the last resort for ornamentals and is not recommended on food crops. Avoid using formulations that contain piperonyl butoxide, which is currently being evaluated for its carcinogenicity.  Pyrethrins are the individual chemicals found in pyrethrum. Pyrethroids are a new array of synthetic chemicals, such as cyfluthrin and cypermethrin. They resist breakdown, thus negating their major environmental advantage. With the three names being so similar, they can easily be confused. Pyrethrum is the least hazardous.



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