EC 627 Reprinted August 1997 Controlling Carpenter Ants J.D. DeAngelis and J. Capizzi

Carpenter ants are serious from view, unless their mines pests of buildings in Oregon, are broken open. particularly west of the Cascade Reproductive termites are Mountains. Although they brown, thick-waisted, and normally excavate in logs, have long wings, approxi- stumps, and hollow trees, these mately equal in length. The ants become pests when they antennae of termites are short move indoors. DATE.and straight (those of ants are Unlike termites, carpenter angled). Termites fly during ants do not eat wood, and so warm, humid evenings in the they kick out the sawdust-like fall. chewings during nest building. OF This is a sure sign of carpenter ant infestation; termites do not make sawdust. What carpenter Carpenter ants do not restrict ants do their nesting activities to wood. Carpenter ant worker Winged OUTcarpenter ant They can establish nests in any Carpenter ants commonly material they can bite into— tunnel in building timbers. insulation, paper, bark, and IS With a longstanding infesta- wood product mulches are just tion, damage may require a few examples. extensive repairs. Usually, Nests even have been found only minor repairs are needed. in stored clothing and sleeping If you find the infestations bags. In some instances, these soon enough, all that may be ants will carry nest-building needed is to get rid of the ants. material, such as fir needles, information: New colonies are estab- into a wall space or attic. lished either by a lone queen or by migration of an existing colony. The latter is common in houses. Colonies disturbed Signs of by the clearing and grading of infestation building sites often migrate. Houses near woods are most Termite worker Winged termite • Ants foraging around or in current likely to become infested. Usually, carpenter ants the home PUBLICATION wings that extend beyond the enter a house through • Piles of sawdust-like borings tip of the abdomen. The front openings around the founda- visible under porches, in How to wings are much larger than the tions. They seem to prefer rear wings. basements, or emerging from recognize them moist, rotting timbers, but cracks or crevices between Carpenter ants frequently most they will readily mine sound, walls and partitions Carpenter ants are large are confused with dampwood THIS dry wood any place in a black or red-and-black ants. termites. Both insects live in • Slit-like holes in woodwork, house. Ants may enter The size varies in workers colonies and mine wood. especially window and door 1 1 through plumbing or wiring For from ⁄4 to ⁄2 inch; queens are Since they are controlled in casings 3 access points, or they may larger, up to ⁄4 inch. Ants different ways, it is important travel into the structure from • Large winged ants in the have a constriction (thin to distinguish between them. trees hanging over the roof. house in late winterhttp://extension.oregonstate.edu/catalog and waist) between their thorax Termite workers are spring (where legs originate) and yellowish to grayish white, up 3 • Faint rustling sounds in abdomen. If winged, there are to ⁄4 inch long, short-legged, walls, floors, or woodwork two pairs of membranous rather slow-moving insects that spend their lives hidden Jack DeAngelis, Extension entomologist, and Joseph OREGON STATE UNIVERSITY EXTENSION SERVICE Capizzi, Extension entomologist emeritus; Oregon State University. Consult your county office of the OSU Extension Service or a current edition of the PNW Insect Control Handbook regarding specific pesticide recommendations for indoor and outdoor use.

How to prevent infestation Carpenter ants mine building timbers, causing serious damage if they’re unchecked. A tightly constructed house with concrete foundation, Among the commonly good clearance, and a full mined portions are porch Ant control basement with good ventila- pillars and supporting tion is least subject to infesta- DATE. timbers, sills, girders, joists, If you locate a nest, you can tion. studs, and casings. The ants remove it with a vacuum often establish colonies in cleaner, then dispose of the • Remove logs, stumps, and masses of fir needles or other bag outdoors. Unfortunately, waste wood near andOF under refuse within walls, under you can’t always find the nest the house. floors, in attics, and in other or nests. If this is the case, • Destroy all known colonies undisturbed places. control is indirect. Place of carpenter ants Carpenter ants are destruc- insecticides very carefully, to within 100 yards or tive in several other ways. form chemical barriers that so of the house. They occasionally damage foraging ants must cross in OUT • Do not bring telephone poles. They damage their search for food. boxes and other wood products The ant then contaminates fuel wood infested with in storage. By mining in the its body with the insecticide IS carpenter ants into heartwood of living cedar and carries it back to the nest, trees, they cause much of the where other ant stages are the house. “wormy” lumber that must be poisoned. Slow-acting, • Do not build over stumps, discarded. Similarly, they persistent insecticides are best logs, or sizeable pieces of mine and weaken orchard and suited for this approach. wood. ornamental trees. They girdle Insecticidal dusts often areinformation:• Check for signs of ants and kill young conifers in used between walls (in wall annually since presently forest plantations. By tending voids), in attics, and in other registered insecticides do aphids for honeydew, they areas where water-based not offer long-term protec- encourage these garden or sprays might cause moisture tion. A structure may be ornamental pests. problems and where emulsifi- reinfested. Besides being destructive, able sprays (with strong carpenter ants in houses are a solvents) might harm fabric, nuisance, crawling over wallpaper,current or tile. Treat the things, getting into food, and line where your foundation Use insecticides safely! periodically swarmingPUBLICATION in the meets the soil. Treat it inside, living quarters. if you can reach it through a • Read the manufacturer’s label carefully and follow the crawl space; treat it outside, instructions. along the walls and entries. • Avoid contaminating food. most • Do not use household sprays near an open flame. • If household emulsifiable sprays get on asphalt tile floors, THIS wipe up immediately. • Store all insecticides out of reach of children and pets. For • Empty insecticide containers completely. Rinse empty containers and use rinse water in spraying. http://extension.oregonstate.edu/catalog This publication was produced and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Extension work is a cooperative program of Oregon State University, the U.S. Department of Agriculture, and Oregon counties.

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