By Dan Suiter
University of Georgia

In nature, it’s mating season. The birds are chirping and
starting to mate. All the critters are doing their thing. And in
April, out come the carpenter bees.

This family of bees has a number of species, all with pretty much
the same biology. In the next couple of weeks, we’ll start seeing
a series of behaviors in these bees, culminating in a
mating-and-egg-laying process.

The unfortunate part of this is that it involves wood structures.

A typical piece of wood that’s susceptible to infestation by
carpenter bees is unfinished, soft wood, such as pine or fir.
Cedar’s highly susceptible.

Old-timers

The bees you’ll see buzzing around wood during the next few weeks
were born a year ago. They left their nest sites, dime-size holes
chewed into the wood, last summer. They went out into the garden
and started doing their pollinating thing as all bees do.

When it got cold last fall, they returned to the same nest sites
and went to sleep for the winter.

Around the first of April, the bees wake up and emerge from the
wood. The bees you’ll see in the next couple of weeks are the
ones doing the mating and laying the eggs. These bees were born
last summer and will be dead by May.

But first…

The females will chew a new hole into the wood, then make either
a left or right turn and chew another section of wood, probably 6
or 8 inches long.

They’ll lay an egg, put some pollen on it, then back up and wall
it off. Then they’ll lay another egg, put some pollen in there,
wall it off and repeat that with six or eight eggs. When they
finish, they live for only another couple of weeks.

The bees you see in the summertime are their progeny. It’s their
kids in the garden during June, July, August and September.

Give ’em an inch…

These bees will return to the hole where they were born to
survive next winter. They come back to the same sites year after
year after year. So if you don’t abate this problem, you can wind
up with significant damage, especially in barns and outbuildings
where you’re not keeping watch.

Not only do you have aesthetic damage with those dime-size holes,
but you have a degradation of the structural integrity of the
wood.

The bees come back year after year because they’re all the same
family. It’s the progeny after the progeny after the progeny. So
you have to break that cycle of reinfestation after reinfestation.

What to do

The University of Georgia Cooperative Extension recommends two
options to kill the active bees in the spring:

• Apply an insecticide dust, such as Sevin, directly into the
  hole in mid to late April. Apply it when the wind isn’t blowing,
  and wear a particle mask and gloves.
• Spray a liquid insecticide on the wood surface every two
  weeks at least through April and maybe into May, as long as the
  bees remain active. Any product that ends in “thrin,” such as
  cypermethrin, cyfluthrin or deltamethrin, should work well. Don’t
  spray the liquid on top of the dust or you’ll negate the efficacy
  of the dust by getting it wet.

Patience

The only time when you don’t have any bees in those wood
galleries is from midsummer to early fall. That’s the best time
to plug up the holes. If you plug them while bees are still in
there, they may actually, when they develop, chew their way out,
leaving more holes.

So wait until probably July or August to plug the holes with wood
putty. Sand them off and then paint that surface with either an
oil- or polyurethane-based paint. Something that’s really thick
will keep the bees from coming back.

(Dan Suiter is a Cooperative Extension entomologist with the
University of Georgia College of Agricultural and Environmental
Sciences.)