Ignore the sawdust, carpenter bees should be left alone

A carpenter bee collects pollen from a daisy on June 23, 2010, in Cincinnati.
A carpenter bee collects pollen from a daisy on June 23, 2010, in Cincinnati. Associated Press

With the decline of honey bees in recent years, pollinators like carpenter bees have tried their best to take up the slack.

They've been given a bad name because of their tendency to use our wood for their brood cells, but they really cause nothing more than cosmetic damage. It takes a large number of carpenter bees a number of years of repeated colonization to actually cause structural damage.

Woodpeckers are more likely to do more damage to your home than carpenter bees. Of course, this doesn't stop people from panicking when they see the sawdust starting to pile up.

It's the females that do the boring. They chew a one centimeter (half inch) hole in a protected spot. She'll bore in five centimeters (two inches) then take a 90-degree turn inside the wood. Following the grain of the wood, she then establishes a series of cells from from ten to 15 cm (four to six inches), sometimes longer.

The male stays outside the brood cells bringing the female food and guarding her nesting site (it’s the males that come to investigate you when you get too close to the nest). Inside the tunnel she's made, the female places large pollen balls that serve as food sources for her offspring. She'll deposit one egg for each pollen ball then seals off each section with a screen of chewed wood.

The female lays additional cells in this manner until the tunnel is completely filled. This usually means six to seven eggs. The last egg laid is the first to hatch (were it the other way around, the young carpenter bee at the end of the tunnel would have to bore through the other cells to emerge from the nest).

After laying her eggs, the mother dies in a few weeks. The larvae develop in five to seven weeks. New adults emerge in late summer.

To keep carpenter bees from chewing up your wood, you have to keep exposed wood surfaces painted or stained. If the bee can't figure out if it's wood, they won't try to bore into it. If you find any holes bored by the bees, run a pipe cleaner or other flexible wire into the gallery. This will puncture the cells; exposing the larvae to the environment where they will die.

Seal up any galleries that have been formed with caulk. Treating each nest with insecticide can be somewhat labor-intensive, but it will work over time.

A better method may be to apply a wood treatment such as Tim-Bor. This particular pesticide is borate-based and is designed to keep wood-boring insects from getting into wood.

If you can tolerate the hole or two they make in your wood, I say leave the carpenter bees alone. Their ability to pollinate our gardens more than makes up for the little damage most of them will do.

For answers to individual questions, please send a stamped, self-addressed envelope to Tim Lockley, c/o Sun Herald, P.O. Box 4567, Biloxi MS 39535.