Identification and Life Cycle
Carpenter bees (Xylocopa virginica), are also known as “wood bees”. They are non-social bees that are commonly mistaken for bumblebees. Carpenter bees do not eat wood, but the females excavate tunnels in the wood for nesting.
Homeowners often notice carpenter bees hovering around the outside of their homes in search for mates and sites to construct their nests. They prefer bare, unpainted, or weathered softwoods found in eaves, window trim, facia boards, siding, decks, outdoor furniture and playsets.
They are approximately 3/4 to 1 – inch length. These large bees are black and yellow in color. Its thorax is covered with yellowish hairs and the abdomen is shiny black and hairless. The males have a yellow area on their face and do not have stingers.
In April or May, after a female carpenter bee mates, she will often use the same nesting site, or tunnel a new one into wood. The tunnel, where she lays her eggs in a series of small cells, may be a foot or more in length. The female then places nector and pollen she has collected in each cell on which a single larva feeds. She can lay between one to six eggs and sometimes up to thirteen. In late summer the larva pupates in its cell and emerges as an adult. The new adults then leave the nesting holes to feed on nectar and return to hibernate during winter.
Habits and Damage
Carpenter bees construct their nests in trees or framed buildings. They usually bore nesting holes in unpainted wood that is perfectly round, about 1/2-inch in diameter.
The males and females are territorial and will defend their nest sites. It is the female bees who sting when disturbed, not the males. The males do not have stingers. Bee stings can cause a life-threatening allergic reaction in some individuals, so never attempt any control measure if you have a known allergy to insect stings.
A single nest can cause minor damage, but continued boring over several years may weaken some wooden structures. Also, insect-eating birds, such as the Woodpecker, can be enticed to feed on larvae and create more damage to a structure.
CARPENTER BEE HIGHLIGHTS
- Nesting Holes. The female bee tunnels into wood to lay her eggs. A yellowish residue can sometimes be found below the hole.
- Sawdust. Wood is chewed and then pushed out of the entranceway of a nesting hole.
- Hovering Bees. The bees are commonly seen near a home’s exterior looking for mates & nesting sites.
- Scraping Sounds. This can be heard from inside the building, caused by bees chewing though wood.
Prevention and Management
The best strategy for carpenter bees is prevention. An Integrated Pest Management (IPM) program can help control bees by targeting the most common sites that these insects are attracted to.
Carpenter bees prefer to nest in soft wood that is untreated, bare & weathered. To manage an existing problem, the following three steps can be taken to rid the bees and prevent the re-use of an old nest.
- Treat. The nesting holes can be treated with an insecticide spray or dust, preferably in the spring when the bees emerge.
- Fill. Abandoned holes can be filled with bits of steel wool or aluminum foil, wood glue or caulk.
- Paint. The wood surface should then be painted or stained to discourage the bees from coming back.
In addition, the following tips are recommended to help prevent or reduce a potential problem with Carpenter bees.
- Paint or varnish all outdoor exposed wood surfaces to protect softwoods from bees nesting.
- Inspect yearly areas that are more susceptible to the bees such as untreated wooden play sets, window trim, fascia boards, siding, wooden shakes & decks.
- When possible, replace exposed softwoods (cedar, pine & spruce), with hardwoods (oak, maple & teak).
- Fill cracks, nail holes & splintered wood with a caulk or wood putty to discourage carpenter bees.
- Carpenter bees emit an odor and create noises that attract other bees, so treat active nesting holes and properly fill and seal them.