Carpenter bees closely resemble bumble bees except for the fact these pests bore into dry wood to make egg galleries.
Bumble bees nest in the ground. Carpenters bees have yellowish hairs over their mid section and a shiny black abdomen that is hairless. The abdomen is the tail-end or last body segment of the insect. Warm weather in April brings out adult carpenter bees to make mating flights around old barns, decks, porches and other areas with weathered wood. Fertilized females soon begin boring new holes to be used as egg galleries.
They usually choose soft wood but seasoned hardwoods and even treated lumber can be attacked. Bare wood is attacked most often but painted or stained wood is damaged when no other suitable nesting areas can be found.
The gallery holes are usually one half inch in diameter. About one inch of gallery is constructed every six days running with the grain of the wood. Galleries can run from 4 inches to 12 inches deep. Female carpenter bees seldom sting but when they do it is extremely painful. Male carpenter bees cannot sting but they are the ones who fly so aggressively toward you when you walk near an entrance hole.
To control them you have to know a little about their habits. After the gallery is completed an egg is deposited with a dab of pollen and nectar. Then the female seals off the egg and food with a plug of sawdust and salvia. This process is continued at the rate of one cell per day for about 6 days. The adults soon die. The eggs hatch into white grubs and then into pupae before becoming adults. This process can take 45 to 60 days.
So applying a pesticide directly into the gallery or hole might agitate a working female or could result in a pesticide gushing back into your face. Use your new knowledge of their habits to control carpenter bees. Use a small piece of flexible wire or tubing to break down the walls between the grubs and to determine if females are present. Large diameter (1/8 to ¼ inch) tubing could crush the working female and allow for deep penetration of an insecticide. A contact or residual insecticide can be used to kill the larvae. Most of the liquid outdoor insecticides (such as Malathion, cyfluthrin, carbaryl) or any of the aerosol spray can insecticides will kill carpenter bees. But due to their chemical makeup none of these products will prevent re-infestation for more than a few days.
There is no magic spray or dust that will keep carpenter bees away. Once a heavy infestation has moved into your house or barn, be prepared to do some work.
Break down the walls between the grubs, apply a liquid insecticide and allow this to air dry for a day or two. The last step is the most important. Use wood dowels, wood putty or caulking to fill the holes and apply a fresh coat of paint. Remember carpenter bees are less likely to attack freshly painted or stained wood.
Tennis rackets or badminton rackets make nice weapons for carpenter bees for the home owner with better eyes, reflexes and joints than me.
Britt West is the extension agent for Barrow County. You can reach him at firstname.lastname@example.org.