Carpenter Bees are
Back at Work
Tim Gibb, Insect Diagnostician, Department of
Entomology, Purdue University
Carpenter bees are
back at it again and the result is a few holes in wood and lot
of people calling for diagnosis and advice.
In order to help them,
we must first learn to translate what they say to what they actually
mean. For instance:
“You have to help me - my
house is ready to fall down” (I have a couple of small
holes in my siding or eaves)
“I have zillions of gigantic, ravaging bees” (I
saw 4 or 5 insects in the vicinity about the size of a bumble bee)
is probably a new mutant exotic pest” (I personally do not
remember seeing them before).
“I have children that I must
protect” (the kids are now out of school and actually pointed
them out to me, otherwise I would not have ever noticed them)
These are almost certainly carpenter bees. A carpenter
bee approximates the bumblebee in shape and size but is nearly
all black and has a much more naked (hairless) abdomen.
descriptions include, a bee working around a nearly perfectly round,
1/2 inch diameter hole in wood, you can be sure that this is a
The hole actually goes straight into the wood
for about 1-2 inches, then makes a 90-degree turn and runs with
the wood grain for some 4-6 inches. The female bee fills 6-8 cells
(separated from one another by partitions of wood pulp) with pollen
Each of these cells contains one bee larva. After
the cells are completed, the female seals the tunnel and soon dies.
Larvae inside the cells mature by late August and new adults emerge
by early September. These adults forage for nectar but eventually
reenter the tunnel (or a nearby one), clean it, and then overwinter
in it. The cycle starts anew the following spring.
Note that carpenter
bees may refurbish an existing tunnel instead of boring a new one,
that an infestation may persist for several years or more, and
that new tunnels are often constructed near old ones.
bee actually causes little serious damage, although continuous
tunneling over many years may eventually weaken the structure.
Perhaps the biggest problem is the annoyance and fear associated
with the large carpenter bee. Males patrol the area and often fly
about the faces of people; however, they cannot sting. The females
do not defend their nest, but can sting if handled.
woodpeckers are attracted to the tunnel looking for a free meal.
Their damage to the wood in trying to get at the bee larvae inside
becomes much more serious than the hole created by the bee.
can be safely and effectively accomplished by dusting into the
tunnels with 5% Sevin, leaving them open for a few days and then
plugging the opening with a dowel or wood putty to discourage future