Published on 05/19/99

Tiny Carpenters' Work Destroying Property

C. Roach, UGA CAES
YOU'D THINK THEY BUILD, like their name implies, but carpenter bees can cause a lot of damage in wood siding and facia board. UGA scientists say the troublesome bees drill an inch into the wood, then tunnel along with the grain for 4 to 6 inches. They often reuse the same area, and tunnels may reach 6 to 9 feet.

Carpenters bees are hard at work in Georgia houses. For all their industrious drilling, though, they have little benefit to people, say University of Georgia experts.

"They have little beneficial effects to offset their more obnoxious habits," said Keith Delaplane, a UGA Extension Service entomologist.

Good at some things, really good at one thing in particular

"They aren't very good pollinators, and they're actually flower robbers," he said. "They suck out the nectar from a flower without pollinating it. They have short tongues and have to bite through the flower to reach the nectar. About the only thing they are good pollinators for is passion fruit."

What they are good at is chewing holes in eaves. "If you get a long-lasting population, they could weaken the timbers," Delaplane said.

What to look for

C. Roach, UGA CAES
SAWDUST MAY BE THE FIRST SIGN OF DAMAGE (lower left corner.) Once you see it, treat quickly to prevent reinfestation. For any treatment to work,though, it must be squirted into each hole. Night treatments are most effective because that's when you can be more sure adults are in their hole.

Carpenter bees look like bumblebees, except they don't have any yellow on their abdomen. They're black with areas of yellow hair and are usually about an inch long. Usually found in porch ceilings, window sills, door frames, headers and siding, they fly or hover without regard to people around.

The troublesome bees chew half-inch round holes in wood. Usually, the first noticeable sign of an attack is the sawdust. They don't usually drill in decayed wood or wood with bark. They prefer soft woods like southern yellow pine, white pine, California redwood, cedar, Douglas fir and cypress.

They drill an inch into the wood, then tunnel along with the grain for 4 to 6 inches. They often reuse the same area, and tunnels may reach 6 to 9 feet.

Causing problems

"Over the long term, it is possible for them to do severe damage," Delaplane said. "They nest in the same tunnels year after year. Each generation carves its own nest partitions. They chew the inside of the tunnels and make paste to create their own nests."

Since they have very little environmental benefit, control is a homeowner's best option.

Controlling bees requires two things

"They're fairly easy to control," Delaplane said. "It requires a ladder and pressurized insecticide."

C. Roach, UGA CAES

Spraying insecticide on the wood surface won't work. You must inject it into each burrow to be effective.

"You can spray any time of the year, but right now is probably the most effective time because the holes are active and you can tell which holes should be treated," he said. "If you see sawdust or feces, spray."

Delaplane recommends spraying at night to kill the adults and the brood.

"If you spray during the day, the adults may be gone," he said. "And they will just start a new colony."

After injecting the insecticide, plug the holes with caulk or wood putty. "They don't like paint," Delaplane said, "so painting after caulking will help."

Faith Peppers is the director of public affairs with the University of Georgia College of Agricultural and Environmental Sciences.