Carpenter bees can sometimes present a nuisance to homeowners with redwood decks, fences, or other structures on their property. However, with some simple steps, carpenter bees can be gradually removed from redwood structures.
Carpenter bees are generally large and robust and resemble bumble bees. They are drawn to wood structures, such as redwood decks or fences, as they build their nests there. Female carpenter bees bore into the wood to build their nests. These tunnels are generally ½ inch in diameter and about 6 to 10 inches deep and may contain several chambers. These tunnels and chambers may weaken wood structures over time and the holes bored by the bees are generally unsightly.
To prevent over infestation of carpenter bees, homeowners should regularly inspect their redwood structures for small holes indicating boring. When holes and carpenter bees are present, an insecticide should be sprayed directly into the holes. The holes should then be thoroughly caulked. Persistence in spraying and caulking bore holes should result in the bee population reducing over time. In addition, staining your redwood structures with a heavy-bodied deck stain such as Cabots Decking Stain will help make the wood less appealing to the carpenter bees. Clear, natural finishes will have little effectiveness against carpenter bees.
To learn more about managing this common insect, the University of California Agriculture & Natural Resources department has an informative Carpenter Bees article.