Carpenter Bees Around Your Fence: Identification and Control

Large, black bees hovering around a wooden fence in a predictable pattern are likely carpenter bees. Unlike bumble bees, carpenter bees have a shiny, hairless abdomen and nest by excavating tunnels in weathered, unpainted wood. They are important pollinators but can cause cosmetic and, over time, structural damage to fences, decks, siding, and other wooden structures.

Behavior and Life Cycle

Carpenter bees are solitary. Males are territorial but lack stingers; females can sting but rarely do. They emerge in spring (April–May), mate, and lay eggs in galleries. There is one generation per year. They prefer softwoods like cedar, pine, and redwood, especially if unpainted or weathered.

Prevention and Control

• Paint or seal all exposed wood with polyurethane or oil-based paint to deter nesting. Inspect annually as paint deteriorates.
• Insecticidal treatment: In early spring, before nesting begins, apply a labeled pyrethroid insecticide (e.g., bifenthrin, cyfluthrin, permethrin) to wood surfaces. Reapplication may be needed as residues degrade. Professional applicators may use microencapsulated products like Demand CS (lambda-cyhalothrin) for longer residual control.

If the bees are only on the fence and not threatening your home, monitoring and maintaining paint may be sufficient. Significant damage takes years to develop.