Question
Hi, I live in Long Beach, CA and have a forest of very happy white birches in my landscaping (am a horticulturist).  I recently made a stand for my mailbox with an old birch trunk (which had been drying for about a year in the back).  Today I noticed a hole that looks the size of a dime with a pile of sawdust below it.  Now this wood is dead, what is it and will it attack the rest of my beautiful birch trees?  Aghgh, help. Thanks

Answer
Sounds like carpenter bees. Carpenter bees (Xylocopa virginica) are very active from early spring through summer around houses and other wooden structures. These insects bore ?inch wide holes that appear to be perfectly round on exterior wooden surfaces of house siding, eaves, window trim, fascia boards, shingles, decks and outdoor furniture.

They do not infest living trees. so there is need to worry about your trees.

Homeowners often refer to these large, dark colored insects as bumble bees because of their similarities in size and appearance. Carpenter bees nest in excavated wooden tunnels. Bumble bees nest in the ground. Carpenter bees are robust, heavy-bodied bees that range ?to 1 inch in length. The carpenter bee can be identified by having bright yellow, orange or white hairs on the thorax and a black shiny abdomen. The bumble bee has a hairy abdomen, black or yellow in color. The male carpenter bee can be identified by having white markings on the head.

Unpainted, exposed wood is especially attractive to carpenter bees. The most effective deterrent to carpenter bee activities is a painted (oil base or polyurethane) surface. Insecticide additive paints are available which may repel bees attempting to nest. Wood stains provide little repelling action. Nail holes or exposed saw cuts should be filled in with wood putty or dowels and painted. If practical, remove severely damaged wood and replace with chemical pressure-treated wood to deter nest construction. To further discourage carpenter bees looking for potential nesting sites, a homeowner should secure all doors, windows and other building openings during the spring. Non-wood surfaces such as vinyl siding are not damaged by carpenter bees.

Liquid insecticide sprays of a synthetic pyrethroid, such as permethrin, (Spectracide Carpenter Ant & Termite Killer Insect Spray Concentrate), cyfluthrin (Bayer Advanced Power Force Carpenter Ant & Termite Killer Plus Concentrate) and bifenthrin (Ortho-Klor Termite & Carpenter Ant Killer Concentrate) can be sprayed on wood surfaces to reduce carpenter bee activity. The expected residual effectiveness of these insecticides on exterior surfaces is less than 30 days, so re-application may be necessary for long-term control.

Established bee galleries should be sprayed with liquid insecticides or dusts labeled for wasp or bee control. The insecticide spray or dust should be directed into the passage entrance hole to ensure bee contact. These control efforts should be conducted in late evening or at night when the bees are inside the wood tunnels. After 24 hours, all tunnel entrances should be plugged with wood putty, caulking compound or wooden dowels coated with wood glue to prevent re-colonization by other nesting bees. If an insecticide is not used, the trapped adult carpenter bees can excavate new openings