Carpenter Bees
Order:
Hymenoptera
Family: Anthophoridae
Scientific Name: Xylocopa virginica
There are two genera of carpenter bees in the United States, the small carpenter bees, Ceratina spp., and the large carpenter bees, Xylocopa spp. The latter genus is represented by nine species which infest a wide array of plant materials including decayed wood, hollow or pithy stem plants, and sound structural wood. it is the damage to structural wood that earns them their name and concerns the property owner.
Initial damage by these bees is generally minor. However, successive generations may recolonize existing galleries or establish new ones, causing serious damage to wood.
Biology and Identification
Xylocopa virginica, the most widely distributed species, is considered to be the most destructive carpenter bee. The activity of these large bees around structures is often mistakenly reported to the PCO as an infestation of bumble bees. These robust, black and yellow bees have shiny black abdomens, which distinguish them from their look-alike, bumble bees, which have rows of dense yellow hairs across their abdomens.
The male and female overwinter in galleries, emerging in the spring to mate. The mated female often cleans out and expands existing tunnels for nesting purposes. A female may establish a new nest by creating a short tunnel with a dime-sized entry hole (3/8 to 1/2 in., 9 to 13 mm in diameter), perpendicular to the grain of the wood. The female then makes a 90-degree turn and burrows for approximately 6 inches with the grain of the wood. Reused nests may reach 3 meters (10 feet) in length.
The female provisions the nest with "bee-bread," a kidney-shaped mass of pollen and regurgitated nectar. The female then deposits a single egg on the bee-bread and seals off the cell with chewed wood pulp. Approximately 6 to 8 of these brood cells are constructed. The bee's entire development, egg-larva-pupa-adult, is completed in the cell and requires approximately 36 days. By the time the adults emerge in late summer to early fall, the previous year's adults have died.
During mating season (spring), the bees are very active. Although they cannot sting, the hovering males often pose nuisance problems. Females are less active until after mating occurs; however, they will sting if provoked. When foraging for food, the bees serve as pollinators.
Control
Inspection is generally accomplished by observing bee activity. Entry holes are usually found in well-lit, sheltered areas such as headers, roof eaves, porch ceilings, doors, and window sills.
Carpenter bees tend to avoid newly painted or sealed surfaces. Use residual sprays to protect unpainted surface areas where excavation has begun.
Plugging and painting new nest excavations often deter further activity. However, this remedial action will not prevent emergence from completed nests. Well-excavated nests should be treated with a residual insecticide, preferably a dust or wettable powder formulation. The application should be made as deep into the gallery as possible. By leaving the entry hold open for a day or more, adult bees will contact the insecticide as they enter and exit the galleries. Once adult activity ceases, holes should be sealed with putty or doweling and the wood surface painted or varnished. This procedure protects the wood from deterioration and reinfestation. Removal of infested wood and replacement with pressure-treated wood is also an effective procedure.
(Courtesy of the National Pest Control Association.)