Be on the lookout for carpenter bees this month. Carpenter bees are large bees resembling bumble bees that drill holes in wood to make their nests. This becomes an issue when they choose to use your house or outbuildings for nesting locations. These bees are not aggressive (in fact the males don’t sting at all and the females usually only sting if handled) but they can be very intimidating due to their large size and loud buzzing.
People notice carpenter bees when the bees are found hovering around their homes or outbuildings. Carpenter bees often choose to build their nests under eaves, around window trim, or in wooden siding.
Carpenter bees don’t usually cause serious damage but repeat infestations can weaken wooden structures. They are attracted to bare, unpainted or weathered wood and seem to prefer softwoods like cedar, cypress or pine. Painted and pressure treated wood are less likely to be attacked by carpenter bees but they are certainly not immune.
Adult carpenter bees overwinter in the wood inside the old nest tunnels. They emerge in the spring to mate and excavate new tunnels in which they lay eggs. Larvae grow within the tunnels and a new generation of adult carpenter bees emerges from the tunnels in late summer. The longer carpenter bees colonize an area, the more damage will be done to the wood.
Controlling carpenter bees may require multiple approaches. First, paint all exposed wooden surfaces to make them less appealing. Polyurethane or oil-based paints are best. If carpenter bees are still an issue, spray an insecticide like carbaryl (Sevin) or Bifenthrin (Talstar) into the holes and close them with putty, caulk or plastic wood. You may need to treat several times to get an established infestation under control. Liquid sprays of carbaryl or a synthetic pyrethroid (like permethrin) can be applied as a preventive, but these treatments are usually only effective for a week or two.
If carpenter bees are nesting in an area where their damage can be tolerated, remember that they are native pollinators. They forage in early morning and are excellent pollinators of eggplant, tomato, other vegetables and many types of flowers.