Carpenter Ants

Homeowners are frequently startled to find that they are sharing their home with a "family" of large ants known as carpenter ants. These are regular inhabitants of wooded areas where they play a very important role in returning dead wood to the soil. Unfortunately, wooden homes are not exempt from attack and it is by infesting man-made structures that carpenter ants become pests. In most cases, however, an infestation indicates a problem of construction. Moisture and unsound (decayed or decaying) wood are necessary requirements for a successful colony. In spite of the ferocious appearance of the large females, they do not sting; they bite only mildly in self-defense.

Contrary to popular belief, carpenter ants do not feed on sound wood. In fact, they do not actually feed on wood at all but simply chew out coarse sawdust size pieces to make galleries in which to live and raise their young. This "sawdust" is then pushed out of the nest area and is one characteristic sign of an infestation. If between the walls, this may not be visible. Carpenter ants actually leave the galleries in the wood to feed and in the home may frequently make forays to the kitchen in search of crumbs, particularly sweets. They may also go outside the home to feed on various plant and animal matter, plant and insect secretions or other insect larvae. Once infested the galleries honeycomb the wood and may ruin its structural strength. It is important to note, however, that affected wood was likely already deteriorated prior to colonization.

The following steps should aid you in dealing with a suspected carpenter ant problem:

In the Home

Older homes (50+ years) or poorly maintained homes are most suspect.

1. Determination as to whether or not a problem exists.

a. Are ants present? A few ants may be present in any home in a wooded area but may not constitute a problem. These ants wander in and die or they may be coming from firewood stored inside. Only large or frequent numbers should cause concern.

b. Do you find the galleries or the sawdust-like workings?

2. Location of the infestation (nest).

a. Look for the sawdust-like material pushed from the galleries through cracks in the wood or through relatively large (1/8") oval holes. The presence of a flour-like wood powder and "pinholes" in the wood indicate the presence of powder post beetles which require different control techniques.

b. Follow the route the ants take to their colony. If ants are found in the living area, they may be coming from the basement or wall areas through available openings such as around pipes, vents, etc. Ants may also come in form outside the home along wires through soffit or attic vents or through cracks in the foundation. The source may be piled wood or lumber, infested trees or poles, or wood fill. Removal or treatment of infested material should solve the problem. Dealing with infested wood fill is very difficult to remedy short of treating or plugging the runways.

3. Treatment of the Problem.

a. Reduce or eliminate the moisture in the infested area. This can be done by repairing leaks (walls and roof), correcting drainage (cellar and sills) or poor ventilation (cellars, beneath porches, under eaves, within walls, etc.).

b. Replace infested and decayed wood if possible especially if there is some question as to any structural weakness. Do not put sound timbers next to infested ones if possible unless they are treated with a wood preservative.

c. Avoid storing firewood in the home. If necessary to do so, all wood should be used up each season and not carried over inside.

d. Treat with chemicals* if necessary but use extreme caution in doing so to minimize hazards. The primary target of applications should be the nest. Insecticidal dusts which can be tracked into the nest by worker ants can be applied to the galleries and at entry ways. If runways are treated, this should not be done where food is stored or prepared but should be restricted to cracks around sink pipes and furnace vents and around sills and cellar windows. You do not need a visible residue to be effective. Check the label on the formulation you intend to use to be sure it is cleared for your application needs.

In most cases, homeowners should concern themselves mainly with correcting the situation causing the problem. If steps 3a - c are followed carefully, they should eliminate the problem. The use of pesticides may only alleviate the problem temporarily and repeat applications are most often necessary.

Mobile Homes

In recent years it has been increasingly common for carpenter ants to set up housekeeping within the walls, floor and ceiling of mobile homes. Here they live in the insulation and go out to seek food. Apparently, they find the insulation as a suitable nesting material and the humidity as a result of condensation provides the needed moisture. In these cases adequate ventilation is of prime concern both within these confined locations and beneath the mobile home. Insecticide treatment here should be handled on a case by case basis and should be done only with professional advice. Owners of mobile homes in wooded areas should be aware of this problem and seek further advice if needed.

*NOTE: These recommendations are not a substitute for pesticide labeling. Read the label before applying any pesticide. Pesticide recommendations are contingent on continued EPA and Maine Board of Pesticides Control registration and are subject to change.

Caution : For your own protection and that of the environment, apply the pesticide only in strict accordance with label directions and precautions.

MAINE DEPARTMENT OF AGRICULTURE, CONSERVATION AND FORESTRY
Maine Forest Service - Forest Health and Monitoring Division
April 2000