Carpenter Ants

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Please Read: This site contains information about using pesticides. Pesticides can be dangerous if used improperly or carelessly. Always follow label instructions. The pesticide product label is the final word on the safe and legal use of pesticides. Questions about pesticide toxicity can be explored at the National Pesticide Information Center (NPIC). Control suggestions are intended for users in the state of Oregon, USA. Others should consult with local experts before relying solely on this information.

OSU Extension Carpenter Ant Bulletin EC 627

Large ants that nest above ground in cavities. Cavity (nest) excavation can cause damage when it occurs in buildings and homes. Carpenter ants are more important as structural pests in temperate climates whereas termites tend to predominate in warmer, more tropical regions. These ants are scavengers so must forage outside the nest for food. They do not eat wood. For additional information about carpenter ant biology and control options download bulletin EC 627 (see above).

Basic Control

Inspect exterior at least once each year during warm months, morning or evening. Look for ants trailing (moving, more or less, in single file) into or out of the structure. Walk slowly around structure, carefully note ant activity on walls or foundation. Ants found entering or leaving the structure should be collected for identification (just one or two is enough). Contact your local Agricultural Extension office for identification help.
Treat only when active infestations are found. Maintenance treatments are not necessary.
Remove all vegetation in contact with structure. Be sure to check the roof for overhanging branches.
Treat exterior wall voids and perimeter where siding overlaps foundation.
For most homeowners it is best to hire a good pest control company to do the actual applications.

Useful Links

National Pesticide Information Center

Iowa State University Entomology Internet Resources

OSU Extension Service

OSU Extension & Experiment Station Communications (Publications)

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Oregon State University, Corvallis, Oregon 97331

Contact: Neil Bell, Community Horticulturalist, OSU Extension Service, 3180 Center Street NE Room 1361, Salem, OR 97301; 503-361-2671; e-mail: neil.bell@oregonstate.edu or contact: Jack DeAngelis, Extension Entomologist (ret.) at getinfo@livingwithbugs.com.