by Daniel Frank, WVU Extension Service Entomology Specialist
Carpenter bees are a common nuisance pest of wood structures. Although there are several different species of carpenter bees in the United States, the common carpenter bee, Xylocopa virginica, is the most widespread and problematic in West Virginia.
DescriptionThe common carpenter bee is a large black and yellow insect about 1 inch in length. Carpenter bees closely resemble bumble bees in appearance except that the abdomen of a bumble bee is fuzzy with numerous hairs, while the carpenter bee abdomen is black, shiny, and hairless.
DamageCarpenter bees are solitary bees that bore into wood to create nests in which to lay their eggs. Females chew round holes up to ½ inch in diameter and several inches in length into dead, un-decayed wood. Carpenter bees often select nesting sites in coniferous woods such as pine, cedar, or cypress. Nesting by a single pair of carpenter bees is unlikely to cause anything more than cosmetic damage. However, repeated nest building by many bees over successive years can result in structural damage to wood.
Carpenter bees spend the winter as adults within nest tunnels. In the spring, they emerge from old tunnels to mate and begin egg laying activities. Females will prepare nests by refurbishing old tunnels, or by boring into wood to create new tunnels. Tunnels are partitioned into several chambers, each containing an egg and food source (pollen mixed with nectar). Development from egg to adult can take up to 3 months. Adults begin to emerge in late summer, but do not construct new tunnels during this time. Instead, both males and females collect and feed on pollen and nectar from flowers before the weather turns cold. Although females have stingers, they rarely sting unless threatened or provoked. Males often exhibit defensive behaviors, such as flying near people that approach their nest, but do not have stingers and are harmless.
Ensuring that all exposed wood surfaces are well painted or varnished will limit attack by carpenter bees. If there is already an infestation and control is needed there are several options. If carpenter bee numbers are not high, control can be achieved by simply swatting and killing the bees. If this is not possible, or if bee numbers are too high, an appropriately labeled insecticidal spray or dust can protect wood from carpenter bees. Insecticide treatments are most effective when directly injected into each nest entrance hole, and when applied to the adjacent wood surface. A number of pyrethroid insecticides (e.g. bifenthrin, cyfluthrin, deltamethrin, lambda-cyhalothrin, permethrin, etc.) are available to homeowners and licensed pesticide applicators for control of carpenter bees. Repeated applications are generally needed to maintain a lethal dose of the insecticide throughout the spring and early summer when bees are most active. In addition to insecticides, carpenter bees should be prevented from entering existing tunnels. Entrance holes should be sealed thoroughly with wood putty or caulking compound. If possible, filling the entire tunnel system with a sealant can also be effective. It is best to wait at least 24 hours after treatment with an insecticide to seal entrance holes. When managing for carpenter bees it may be helpful to treat and seal entrance holes during the early morning or late evening when bees are less active.
Balduf, W. V., 1962. Life of the carpenter bee, Xylocopa virginica (Linn.) (Xylocopidae, Hymenoptera). Annals of the Entomological Society of America Vol. 55(3). Pp. 263-271.
Jones, S.C. Carpenter bees. Fact Sheet, HYG-2074-06. The Ohio State University.