In the late-spring and early summer, homeowners often notice large, black bees hovering around the outside of their homes. These are likely to be carpenter bees. Carpenter bees overwinter as adults in wood within abandoned nest tunnels. They emerge in the spring, usually in April and May. After mating, the fertilized females excavate tunnels in wood and lay their eggs within a series of small cells.
Carpenter bees prefer to attack wood which is bare, weathered and unpainted, especially redwood, cedar, cypress and pine. Painted or pressure-treated wood is much less susceptible to attack. Wood stains and preservatives are less reliable than painting, but will provide some degree of repellency versus bare wood.
Liquid sprays can be applied as a preventive to wood surfaces which are attracting bees. Residual effectiveness of these insecticides is often only 1-2 weeks, however, and the treatment may need to be repeated. Pesticides placed inside previously drilled holes will last longer, but the damage has already been done. Consequently, the best deterrent to Carpenter bees is to paint all exposed wood surfaces.
