Carpenter Bees - Xyclopinae

Carpenter Bees - Xyclopinae

Have you noticed some perfectly round holes in your wooden siding, deck or other areas of your home, that have happened not by you doing so, or from a mischievous child? Perhaps this is late-spring, early summer and you happen to see some large black bees hovering around outside your home. They are roughly the same size or little bigger than a bumblebee, but these are probably carpenter bees searching for a mate and looking to make nests in those round holes that have been bored into your structure. They can be quite destructive, as once they have bored into the wood, they will turn in 90 degree angles to the left and right to carve out areas to make cells for their offspring.  Carpenter bees prefer softwoods like redwood, cedar, cypress and pine. If these are left bare, unpainted or are weathered it is like an open invitation to the bee to make their nest. Painted or pressure treated wood will also be used, but they are less likely to go to these types of wood if there is other more desirable wood present. The most common areas that they will bore into to make nests are eaves, window trim, fascia board, siding, decks, and outdoor furniture.

Carpenter bees will overwinter in abandoned nest tunnels and emerge in the spring around April or May.  The female will clean out old nests or will excavate new nests and tunnels after mating, so that she can place her fertilized eggs into sectioned off cells with food for the larvae to feast on until they emerge as adults in late summer.

The male carpenter bee will protect the nest, but are quite harmless as they lack stingers. The female carpenter bee can inflict a painful sting, but rarely do unless someone tries to handle them. The upper surface of their abdomen is shiny black and does not have hair like the bumblebee, and they usually do not have the yellow marking of a bumble bee, but may have some yellow on the face or body depending on the type of carpenter bee.

Carpenter bees do not consume the wood as food. They simply excavate the tunnels for nesting sites. Newly formed tunnels made by carpenter bees will have tell-tale signs of formation by the coarse sawdust that is left below the perfectly round hole (roughly ½” in diameter) that the carpenter bee has made. The entrance holes go into the wood about ½” or more then will turn horizontally and follow the wood grain.  The galleries will typically run for about six to seven inches, but have been known to exceed 12”, probably by the re-use of nests from year to year.

Preventing carpenter bee damage is difficult.  Use of a residual spray, helps and will keep working on the wood for an extended amount of time as the carpenter bees are active over several weeks. Treat all tunnels with a liquid or a dust, since what is seen is not the full scope of how large these tunnels are and all the areas need to be coated. Sometimes it just is not practical to treat every single area of wood on a home. Dusts work well in the voids as they will coat all the areas of the tunnels with relative ease.  Once the tunnels are vacant (usually after treatment within 24-36 hours) it is important to seal the entrance points with a ball of steel wool or aluminum foil and to caulk or use wood putty so that the tunnels can’t be used for overwintering by adults.  If you try to plug untreated holes, you may just end up with more holes if the adults are still in there, since they will just chew another exit hole to get out.

It is always best to have an experienced pest control operator to come and assess your problem and give you helpful guidance and recommendations as to what is best for your particular problem. As with all pest control products, make sure that they are labeled to be used in your particular area or state. If you are a do it yourselfer, make sure to follow label instructions implicitly for your safety as well as the environment.