In the spring and early summer, homeowners often begin noticing large, black carpenter bees hovering about, seeking out mates and favorable construction sites for their nests.
While male carpenter bees are quite aggressive, hovering in front of anyone who lingers around a nest, they are actually rather harmless because they lack stingers. Females, on the other hand, can inflict a painful sting if they are instigated or feel threatened.
Carpenter bees are distinguishable by their bare, shiny, black upper abdomen. They bore into wood to lay eggs, their preference being bare, unpainted or weathered softwoods – especially those located on eaves, window trim, fascia boards, siding, wooden shakes, outdoor furniture and decks.
The best way to deter carpenter bees is to paint all exposed wood surfaces, especially any with a history of being attached. Wood stains will provide a certain degree of repellency versus bare wood, but paint is the most dependable. Garages and outbuildings should also remain closed during nesting season to further deter nesting.
According to Mike Klahr, Boone County’s Extension Agent for Horticulture in Ohio, “Liquid sprays of carbaryl (Sevin), or a synthetic pyrethroid (e.g., permethrin or cyfluthrin) can be applied as a preventive to wood surfaces which are attracting bees. Tunnels which have already been excavated are best treated by puffing an insecticidal dust (e.g., 5 percent carbaryl or Sevin) into the nest opening. Aerosol sprays labeled for wasp or bee control also are effective. Leave the hole open for a few days after treatment to allow the bees to contact and distribute the insecticide throughout the nest galleries. Then plug the entrance hole with a piece of wooden dowel coated with carpenter's glue, or wood putty, and paint over it. This will protect against future utilization of the old nesting tunnels and reduce the chances of wood decay.”