Branches litter the streets, and trees are strewn about the neighborhood like broken matchsticks. These are the familiar sights following a hurricane. Then comes the expense of cleanup. One might be tempted to cut corners in restoring order to a homestead or general neighborhood. These actions might serve well temporarily, but they may soon give way to a greater nuisance. In the span of a few months, tiny piles of shavings and trails may appear. The new nuisance that has arrived to wreak further havoc upon a storm-damaged homestead is known as the carpenter ant (Table 1).

Carpenter ants have at least 1,000 valid species with 54 subgenera, and seven of these occur in North America. Out of these seven, the structure-infesting species occur in the subgenera Camponotus, Myrmentoma, Tanaemyrmex, Myrmobrachys and Myrmothrix. The majority of the important species occur in the subgenus Camponotus.

The common name of carpenter ants comes from the preference for dwelling in and excavating wood. Carpenter ants are the largest ants found invading homes for foraging or nest-building. Upon examination, a wooden nesting site will often resemble an ornate carving of smooth tunnels representing ant galleries, and its interior will often have a sandpaper texture. Carpenter ants will ordinarily excavate portions of wood softened by decay, water or by the presence of other insects. However, they also like to take refuge in sound wood, such as firewood, and this may lead to a convenient home invasion.

Main carpenter ant colonies are commonly found in trees surrounding an infested structure. Tree hollows, tree holes, stumps and dead limbs are the most typical nesting sites. Satellite colonies can be found in similar conditions in the same tree or in one or more neighboring trees. The main ant colony affecting a home will usually be located outdoors. Indoors may play host to a number of satellite colonies (Table 2). They nest in various wall voids or in hollow curtain rods, shower rods, hollow doors, hollow columns, behind dishwashers, under insulation in both attics and crawlspaces, under cabinets, in floor joists, attic rafters, soffits/furdowns, and ceiling voids next to skylights and chimneys.

A sign of an infestation is when swarms of winged ants emerge from walls in early spring and try to escape through the windows. This is a sure sign of trouble because the main part of the colony is being left behind. A faint rustling sound in the walls, floors or woodwork also indicates the presence of carpenter ants. The workers will make slit-like openings through the surfaces of infested wood and expel their borings through these openings. These fibrous piles of sawdust, known as frass, frequently are found within basements, dark closets, under porches and various other innocuous places. Some colonies may even place these piles several feet from a nest’s location. Interior nests may be within voids or beneath the insulation of structures. Infestations can also occur in outdoor appliances such as air conditioners and heat pumps.

Colonies are initially started by a solitary queen. She begins the nest beneath a rock, in soil or a tree hole, in an insect-bored tree tunnel, etc. She lays only a few eggs, which will eventually hatch into tiny workers known as minims. Their sole purpose is to forage or find food for the queen and her young. The largest workers may soon lay eggs that will only produce male ants. Upon mating, the queen will either create or find a smaller chamber in which she will remain with her brood until they are adults. This can take anywhere from two to 10 months.

Carpenter ant colonies produce winged male and female alates (swarmers or winged adults) that fly out to begin new colonies. These alates are produced in the colony after three years and will produce swarmers every year after. By that time the colony includes more than 2,000 workers. Alate swarms typically occur in late spring and early summer, although some alates have been observed emerging around the first of July.

Large colonies can be categorized by winged males and females during the winter. These winged sexuals may be produced over a single summer or winter within the parental nest, although the larval stage may be of longer duration during the winter. The ants are able to withstand cold because their bodies generate glycerol, considered a natural antifreeze, whenever temperatures fall to a certain point. Once mature, they may leave the nest for nuptial flight from May to July.

Occasionally, swarms inside structures are males only. Such swarms may be the brood of an unfertilized queen within the colony, or they may be excess males that have been evicted by workers in the colony. The swarms found inside homes are often from satellite colonies where alates are either moved or developed from pupae that have been carried from the main colony. These swarms usually include fewer than 100 alates, although larger swarms may occur. Sporadic swarming may also occur with a few alates appearing several days or weeks in a row. Such swarms may be the result of changing environmental conditions including sudden rains, changing temperatures…even hurricanes! These ants show some preference for moist, rotting timbers about the foundations but will readily mine sound, dry wood anyplace in a house. In interviews with pest control companies, 79 percent reported a 25 percent or less association with actual structural damage because of carpenter ants.

In suitable conditions, the nest will thrive and the queen will lay more eggs. It should be noted, however, that satellite colonies will contain mature larvae and pupae, workers and winged alates, but they will not contain eggs or queens. Despite a lack of eggs, these satellite colonies may still have an opportunity to nurture other potential pests. Carpenter ants have been known to attend aphids and other honeydew-secreting insects and protect them from predation, thereby increasing numbers of pests. In spring and early summer the ants prefer proteins, but they begin in July to regularly feed on sugar-based foods and carry the practice into winter. If the ants were to join forces with other species of insects, this could become quite problematic for a homestead.

Another major problem is when humans encounter carpenter ants. These large ants do not sting but will bite and spray formic acid. This can damage skin, causing peeling skin with raw skin beneath.

The primary way to control infestations of most pest ant species is to find and directly treat the colony with an appropriate contact insecticide or bait. Typically, only 5 to 10 percent of an ant colony is out foraging at any one time, so treatment of foraging trails with fast-acting contact insecticides leaves most of the colony alive. Time and energy spent in tracing foraging trails is well worth the effort; without it, return trips for extra treatment will often be necessary. It would be wise to examine a considerable amount of suspected infested property and neighboring properties; carpenter ants have been noted to forage as far as 300 feet away from their nests.

When an infestation is longstanding and the colony is a large one, consisting of many thousands of ants, structural damage is frequently extensive enough to require major repairs. Pest control personnel across the country reported that carpenter ants are the most frequently encountered and problematic ants that result in numerous repeat services. In four eastern states, 20 percent of pest control companies completed more than 40 jobs for carpenter ants each year, and 50 percent required return visits. Most ant infestations originate outside of buildings. A pest management professional experienced in ant control can most times quickly locate the source(s) of ant infestations. The best strategy for long-term results is to address the sources directly and correct contributing conditions.

Proper identification of a suspected pest ant is crucial to the successful control of the infestation. Identification allows the pest management professional to know the habits of the ant involved so the nest sites can be quickly located and properly assessed to know whether treatment is actually necessary. Once an ant has been identified, an inspection is necessary to determine where the colony is located, where activity is present, whether or not other ant species are present, and whether contributing conditions exist. The client should be consulted to learn when, where and for how long the ants have been seen.

Floor plans of the infested structure or property may be diagramed to assist in developing a clear picture of the infestation. This practice could be highly effective for treating the infestation because of the ants’ habit of following defined trails and guidelines from their nest to food and water sources and thus lead an inspector back to the colony’s location. Finding the initial trail is sometimes difficult and requires patience and good eyes. Ants usually follow structural guidelines for their trails. Such guidelines include edges and corners found on landscape timbers and along sidewalks and edges of brick veneers on homes. Garden hoses and gutters also supply pathways for ants. It should also be noted that carpenter ants are night foragers, and that a night inspection might be helpful for a chronic, stubborn infestation.

If ants are not easily found, it may be useful to place food materials in suspected areas to help locate the ants. This practice is commonly known as food baiting. Food baits can then be replaced by insecticidal baits that capitalize on the ants’ behavior of bringing food back to the satellite and central nests to feed the brood and the queen. This method works well for many species of ants and, despite the time lapse, such efforts may assist in developing a treatment plan. This practice can also be more effective when used in combination with other treatment measures. It should be noted that carpenter ants are usually difficult to control with baits, and it is always best to attempt to locate and treat these colonies directly whenever possible. Recently, however, effective carpenter ant baits have been developed. The treatment used depends entirely on where an ant colony is located. New nonrepellent insecticides can be applied on active trails and along known guidelines. A professional must be able to use his or her experience to correctly diagnose and treat an infestation (Table 3).

After hurricanes, it is best not to ignore little problems such as stumps that might lead to carpenter ant or other ant infestations. Grinding stumps and distributing the shavings as compost or mulch and carefully checking the property for other contributing conditions will pay off. It may prevent a pesky and pricey infestation.

Table 1- Contributing Conditions for Carpenter/Pest Ant Infestations

Trees and shrubs resting against a structure’s wall or roof/sheathing

Untreated stumps and dead tree limbs

Plumbing leaks; roof and window leaks

Inadequate drainage along foundation

Moisture-damaged wood or excess condensation

Inadequate attic and crawlspace ventilation

Exterior cracks and holes around windows, doors, and furdowns/soffits

Clogged gutters

Firewood placed near homes or on the ground; wood/soil contact

Available food sources indoors and outdoors (sanitation issues)

Landscape mulching thicker than two inches

Piles of lumber, bricks, stones, debris, leaf litter, etc.

Tree holes

Table 2- Sites for Satellite Colonies

Hollow porch columns

Above porches and dormers

Above/below bay or box windows

Soffits/furdowns, especially those with no vents

Hollow curtain or shower rods

Hollow core doors

Upholstered furniture

Stored cardboard boxes

Wall voids below and above windows

Wall voids above doors

Wall voids around fireplaces

Ceiling voids around skylights

Hollow ceiling beams

Under bathtubs

Under showers

Under hot tubs

Under crawlspace and attic insulation

In false ceilings in basements

Table 3- Tips for Successful Baiting for Ants

Consistent supervision of baits

Place baits close to colonies and/or near trails; placement in electric outlet boxes in walls

Remove extraneous food sources

Do not place baits near insecticide-treated areas or on treated surfaces