We've been getting a lot of calls about big bees lately. These are carpenter bees. They winter over as adults and cannot sting. They tunnel into wood, producing round holes about a half inch wide, and lay their eggs. The eggs develop through the summer and the young adults spend the winter in the tunnels. The following spring the cycle begins again.
These bees prefer to attack wood that is bare. The best way to avoid an infestation is to keep all exposed wood surfaces painted. Once an infestation has been detected the tunnel entrances can be treated with an insecticide. We recommend Hi Yield 38 Plus Turf, Termite, and Ornamental Insect Control. Treating at night is more effective. Holes should be left open for a few days to allow bees to come into contact with the insecticide. Then the holes can be plugged to prevent further use by carpenter bees.
Information courtesy K-State Research and Extension.