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Carpenter Bee (Xylocopa)

- Colorful wood-boring bees -

Summary: Carpenter bees look like bumble bees but tunnel in wood to make a nest. Damage is usually minor but should be repaired.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

What are carpenter bees?

Carpenter bees (right) are large, colorful bees that look somewhat like bumble bees [picture of carpenter bee]. Carpenter bees occasionally construct nests in exterior structural or decorative wood such as siding, fascia boards, trim, and log homes. A round hole is chewed in the wood surface then a tunnel is bored, usually at 90 degrees to the entrance (lower right).

The tunnels may be used year after year, and lengthened each year. Damage is caused by this repeated use of the wood which eventually may weaken it directly or by allowing water to penetrate. Entry holes are round and generally about 1/2" in diameter. Tunnels are excavated by female bees using their powerful mandibles (jaws).

Can I stop carpenter bee damage?

Unfinished wood surfaces are far more likely to be attacked than finished wood. Paint works better than stain to resist carpenter bees but stain is better than no finish. Bottom line - the heavier the surface finish the better. Softer wood is generally selected and surfaces in direct light, as opposed to in shadow, are preferred.

carpenter bee
carpenter bee - a bumble bee look-a-like; photo by USDA/ARS
carpenter bee tunnels
Carpenter bee tunnels. Original drawing from Wood-Inhabiting Insects in Houses by Harry B. Moore, 1979. USDA, Forest Service and HUD.
 

Carpenter bee holes should be repaired to prevent bees from enlarging tunnels year after year. If left open these entrance holes may allow water and rot fungi to attack wood, which in the long run will cause more damage than the bees themselves.

To repair carpenter bee damage you'll need some exterior caulk and an insecticide to treat around the holes. Several insecticides are available for this application. EcoPCO WPX is a botanical insecticide and there are several products that use cypermethrin that are approved for this use, for example Demon WP and Cynoff WP. Since approved usage can change be sure to check the package label for carpenter bees.

Treat around the entrance holes at the approved rate using a garden sprayer, allow to dry for several days then seal the hole with caulk, or a wooden plug, and finish to match the existing surface.

The Pest Management Store

Identification guides, reference and gardening books, etc.

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New botanical insecticides can be safely used indoors for a variety of pests. See label instructions for these applications. As with any insecticide, please read and carefully follow these instructions.


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Jack DeAngelis, Ph.D.

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