Carpenter bees are annual annoyance

Right now is one of my favorite times of the year. The dogwoods and redbuds are blooming, the forsythia and flowering quince are nearing the end of their bloom, and the azaleas are beginning to show their colors.

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All the plants are beginning to grow. When the plants start to flower, it brings a lot of the insects out to feed on the blooms.

A few weeks ago, I wrote about pollinators. The hollies in the area started blooming last week, and the bumblebees and honeybees are covering the plants feeding on the pollen. While they are feeding, they are not aggressive and usually don't pay any attention to you.

However, I did notice one bee this week that can cause problems: the carpenter bee.

These are large, black and yellow and frequently seen in spring hovering around the eaves of a house or the underside of a deck or porch rail. They are often mistaken for bumblebees, but differ in that they have a black, shiny tail section. The carpenter bee gets its name from its habit of excavating tunnels in wood with its strong jaws.

The first sign of these bees is the pile of sawdust on the ground, patio or porch. When you look around, you will find a neat, half-inch hole that looks like it has been drilled into the wood. These bees will drill into any type of wood, even wood that is supposed to be resistant to insects. They will even drill into some painted wood.

Carpenter bees overwinter as adults, often inside old nest tunnels. They emerge in late March through April, with the males usually first. Males can be distinguished by the whitish spot on the front of the face. The males don't have stingers, but they are territorial and will harass other bees and people who venture near their protected areas. Females can sting, but they rarely do so unless confined in your hand or angered.

The bees feed on plant nectar and begin constructing new tunnels in a few weeks. They start on the underside of the wood and drill upward for a half-inch or more. Then the tunnel will turn and follow the wood grain. This is called a gallery. These typically run 6 to 7 inches, but they can be more than a foot.

Sometimes, several bees use the same hole, but they have individual galleries branching off the main tunnel. If the same entrance is used for years, tunnels can extend many feet in the wood.

Inside her gallery, the female gradually builds a large pollen ball that serves as food for her offspring. She deposits an egg near this pollen ball and seals off this section of tunnel with a partition made of chewed wood. She constructs additional cells in this manner until the tunnel is completely filled. She can lay six to seven eggs in a gallery.

These adult bees die in a matter of weeks. The eggs hatch in a few days, and the offspring complete their development in about five to seven weeks. Adults begin to emerge in later summer. Though the bees remain active, feeding on pollen in the general area, they do not make new tunnels. They can be seen cleaning out old tunnels, which they will use as sites to spend the winter.

Carpenter bees do little structural damage to buildings, but the holes and sawdust they produce are unsightly. One problem associated with carpenter bees is woodpeckers, which have been known to attack the wood with the carpenter bee larva inside. There are also wood-decay organisms that can enter the wood through the hole made by the bee.

So how do you keep the bees from boring inside?

Prevention is difficult. Insecticide sprays applied to wood surfaces are effective for only a short time. Because the bees aren't actually eating the wood and are active for several weeks, they are rarely exposed to lethal doses of the pesticide.

Any exposed wood on the house could be attacked, so it is difficult and usually impractical and unsafe to try applying pesticide everywhere. Also, it's not wise to spray the bees while they are flying because you expose yourself to the pesticide.

Treating the holes with insecticide can reduce the use of the hole and possibly kill some of the bees. Products containing carbaryl (Sevin), cyfluthrin or resmethrin, among other chemicals, are suitable choices.

Another option is to practice your tennis strokes. The other day, I was in a hardware store and saw a carpenter bee swatter. It was shaped like a tennis racket and held two or four D cell batteries. It worked on the same principal as a bug zapper. You could practice your backhand and fry them at the same time.

Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at charlesp@uga.edu. The Extension Web address is www.ugaextension.com/columbia.