Carpenter Bees are an annoying insect pest and a somewhat common nuisance to log homeowners. Carpenter Bees resemble bumblebees but unlike bumblebees they use wood for nesting. They nest in wood that is dried and seasoned and prefer softwoods such as pine, fir, cedar, redwood, and cypress. They bore tunnels in the wood to lay their eggs leaving round entrance holes.
Attractive nesting sites include nail holes, exposed cut ends, and bare, unpainted wood. Typical areas of infestation include wood trim near the eaves and gables of a home, log and conventional wood siding, fascia boards, porch ceilings, fence posts, railings, outdoor wood furniture, and non pressure-treated decks.
The best methods of prevention are to keep all exposed wood surfaces well painted or stained using an oil-based coating. To treat infestation, locate the tunnel entrances and apply an insecticide directly in the tunnels and over a wide adjacent area. It's best to treat in the evening toward dusk when its cooler and the bees are less active. Do not immediately seal the entrance holes! This allows the bees to freely distribute the insecticide throughout the tunnels, increasing its effectiveness. If the openings are plugged before the bees are killed, they can chew new openings elsewhere.
Insecticide dusts are more effective than sprays because they readily cling to their bodies and newly emerged bees will contact the dust when leaving the opening. Dusts to use include boric acid, bendiocarb, carbaryl, and pyrethrins. Reports also indicate that mothball crystals are very effective and can be used in a similar fashion as the dusts.
After treatment, it's best to wait until adult activity ceases or until autumn before sealing holes with caulking compound or wood putty and staining or painting. Finally, adding an insecticide paint additive to WeatherSeal will also create another barrier of defense against Carpenter Bees and many other crawling insects such as spiders, ants, wasps, etc.
Use care and take all the necessary precautions when using pesticides. Follow directions and wear proper safeguards such as dust masks, chemical resistant gloves, goggles, etc.