Carpenter bees bore into wood to construct their nests. They are capable of drilling a large number of 1/2 inch diameter (13 mm) holes in preferred sites. Carpenter bees often reuse the same nesting sites year after year. Nail holes, exposed saw cuts and unpainted wood often attract these bees. Porches, garages, shed ceilings and trim, railings, roof overhangs and outdoor wooden furniture are common nesting sites. Continued borings may weaken wooden structures, and the yellow sawdust and waste materials may stain cars, clothing or furniture.
Carpenter bees are large, black and yellow insects about 1 inch (25 mm) long. They closely resemble bumble bees. The thorax is covered with yellowish hairs, and the abdomen is a shiny black color and hairless. Male carpenter bees are territorial; in the spring they are often found guarding potential nest sites. They discourage intruders by hovering or darting at anything venturing into the nesting areas. The female carpenter bee, like many other bees, can sting, but it is uncommon for her to do so; the males do not sting.
Carpenter bees nest in dry wood and occasionally hollow stems. They overwinter as juvenile adults in the tunnels from the previous year. Those which survive the winter mate in the spring (April to June) and then begin nesting activities. They often refurbish old tunnels instead of boring new ones. The tunnel may be a foot or more in length. The eggs are placed in cells; the female places nectar and pollen she has gathered from flowers to feed the young in each cell. The larvae hatch, feed and pupate within the cells. New adults emerge before cold weather in the early fall.
Well-painted, finished structures are a deterrent to carpenter bees. When tunnels are found, treatment with an insecticide and sealing of the tunnel is recommended. Wasp, hornet and bee aerosol sprays are effective and easy to use. The material should be applied in the early morning or after dark on a cool evening (when the bees are less active) to the tunnel entrances and along exposed surfaces. If no activity is observed a few days after application, the holes should be plugged deeply with putty or caulking compound. If the tunnels are plugged without first killing the insects, any carpenter bees trapped inside will bore new openings. Tennis racquets have often been used to successfully control adults.
Site updated January 1, 2017
© 2010-2017 Albert W. Needham