Agricultural publication
G7424 — Reviewed October 15, 1996
Darryl P. Sanders
Department of Entomology, University of Missouri-Columbia
The name carpenter bee
applies to several species of bees found in the United
States. The only one of importance in Missouri is a large
species, Xylocopa virginica (L.), which is widely
recognized as the carpenter bee. Like a bumble bee, it is
about 1 inch in length and black with some markings of
yellow hair. Unlike that of the bumble bee, the top
surface of the carpenter bee's abdomen lacks yellow hair
markings. It is almost hairless and appears to be entirely
black and rather shiny.
Carpenter bees often fly
near eaves and gables of houses. Residents may become
frightened by this activity because male bees patrol these
areas and may fly near people. They are unable to sting.
The females do not actively defend the nest but will sting
if handled.
Habits
Carpenter bees generally are
beneficial insects because they pollinate numerous species
of plants. They may become destructive, however, through
their habit of digging nests in wooden buildings.
People may become alarmed
when holes, about 1/2 inch in diameter, begin to appear in
exposed wood. In addition, unsightly defecation stains are
usually present near these holes.
The entrance hole is a
nearly perfect circle. It usually goes straight into the
wood a short distance, then makes a 90-degree turn and
runs with the wood grain. Several galleries may lead from
a single entrance.
The female builds
individual brood cells in the gallery, stocking each with
pollen and nectar before laying an egg and sealing the
cell. The new bees emerge in late summer, feed and then
re-enter the galleries for the winter. In spring they
reuse existing galleries or build new ones. Infestations
may persist for several years.
While carpenter bees
attack many species of dried, seasoned wood, they seem to
prefer softwoods such as pine, fir, redwood and cedar.
They may damage porch and shed ceilings, railings,
overhead trim, wooden porch furniture, dead tree limbs,
fence posts, wooden shingles, wooden siding, window sills
and wooden doors. They prefer unpainted or well-weathered
wood to painted or hardwood timbers. The wood preferred is
at least 2 inches thick.
Control
Carpenter bees should be
treated after dark when bees are calm, preferably on cool
nights. Use a pressurized can of spray that shoots a
stream of liquid for quick knock-down of bees. This spray
is good only for immobilizing the bees so you can place a
residual (longer lasting) insecticide inside the
galleries. Use only one of the following residual
insecticides:
- bendiocarb (Ficam)
1% dust
- carbaryl (Sevin)
5% dust or 1% spray
- chlorpyrifos (Dursban)
1% dust or 0.5% spray
- cyfluthrin
(Tempo) 0.1% spray
- cypermethrin (Cynoff,
Demon) 0.2% spray
- permethrin
(Flee) 0.5% spray
Dust is most easily placed
in the gallery opening using a hand duster. A flexible
lotion bottle with nozzle makes an acceptable duster. A
pin stream of spray should be used to apply the liquid.
Cotton soaked in one of the liquid insecticides and then
placed into the gallery is an effective application
method. Wear rubber gloves while handling such material.
After treatment, fill the
outer holes with caulking compound, plastic wood or a
tight-fitting wooden dowel glued in place. If paint on the
wooden surface is not undesirable, painting will
discourage further attack by other carpenter bees.
If the bees pose no
particular threat, you might consider delaying preventive
measures, since treating existing nests is easiest and
most effective early in the year. Treat nests before the
bees become active. This way you can be sure that there
are no stragglers outside the treatment area that might
start a new nest at a nearby untreated location.
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