Carpenter bees, also known as wood bees, are a type of larger bees that bore into wood, causing damage to houses. These bees are most active in warmer climates, with lengths reaching up to 1.5 to 2 inches in California.
According to Lynn Kimsey, a retired entomology professor from UC Davis, Carpenter bees prefer to nest in dead or softer wood by excavating holes. The female bees dig nests approximately 6 to 12 inches deep.
“They nest in dead wood by tunneling in, then branching off with side tunnels where they store a mixture of pollen and nectar as food for their larvae before laying eggs,” explained Kimsey. “Each female bee has her own nest with 2 to 10 brood cells.”
The bees reuse nests left behind by previous generations by cleaning out residues and drilling back into the wood along the grain. Over the years, these nests can extend several feet.
Carpenter bees are solitary insects, so each female bee builds and maintains her own nest. They are typically black and shiny with a stinger.
Male bees, on the other hand, do not sting and are more susceptible to predation by birds and other animals. They mainly hover among flowers for pollination and mating and do not stay in the nests. However, they have a strong territorial awareness and often feature bright yellow or orange patches on their backs.
Kimsey advises not to panic if you spot a large black shiny bee in your yard. While female bees can sting, they are not aggressive and would require significant provocation to attack.
To prevent Carpenter bees from boring into wood on your patio, balcony, or other wooden structures, Kimsey suggests covering soft wood with metal mesh or using sealants. If there are existing holes, they can be sealed with caulk.
She added, “The damage caused by Carpenter bees is a slow process and limited to specific areas, so there is no need to worry too much. Significant damage may take several years to occur.”
According to information from the UC Davis Entomology Museum, Carpenter bees are known to nest in fence posts, underneath decks, or below porch railings. While the actual damage may take a long time to manifest, the holes they leave behind can make wood more susceptible to fungal or termite infestations. Experts recommend using oil-based paint or polyurethane to coat wooden surfaces. If possible, damaged wood should be replaced or repaired.
In the wild, Carpenter bees serve as natural recyclers of wood, aiding in the decomposition of dead branches and trees.