The question of whether bees “like” wood is complex. Unlike destructive pests that consume wood for food, certain bee species use it strictly as a medium for nesting and shelter. These bees do not digest wood cellulose, but their powerful mandibles allow them to excavate tunnels. The resulting damage is not from eating but from the physical act of boring, which can weaken structural integrity over time. Understanding the specific species and their behavior is the first step in addressing this issue.
Identifying the Wood-Nesting Bee Species
The primary species responsible for boring into wooden structures is the Carpenter Bee, belonging to the genus Xylocopa. These large, solitary bees are often mistaken for bumblebees due to their similar size and coloration. A key visual difference is the Carpenter Bee’s abdomen, which is predominantly hairless, black, and shiny, contrasting sharply with the fuzzy, hairy abdomen of the bumblebee.
Carpenter bees prefer soft, unpainted, and weathered wood, such as cypress, pine, cedar, or redwood. They commonly target eaves, fascia boards, deck railings, and porch ceilings. Although considered solitary, several females may construct nests in close proximity or share tunnels, sometimes giving the appearance of a social colony.
Other bee species, like Mason Bees and Leafcutter Bees, also utilize wood for nesting. However, these are cavity nesters that do not actively drill. They use pre-existing holes, cracks, or hollow plant stems to build their brood cells. The presence of a newly drilled, perfectly round hole is the signature sign of a Carpenter Bee.
Why Bees Bore into Wood
The biological drive behind wood-boring is purely reproductive, focused on creating a secure environment for their offspring. The female bee uses her strong mandibles to chew into the wood, initially drilling a perfectly circular entrance hole about a half-inch in diameter, perpendicular to the grain. Once inside, the bee changes direction and tunnels parallel to the wood grain, excavating a gallery that can extend several inches or even feet over time.
Inside this gallery, the female constructs a series of individual brood cells. These cells are separated by partitions made from chewed wood pulp mixed with saliva. For each cell, the female collects a supply of pollen and nectar, known as “bee bread,” before laying a single egg. This stored food is the sole sustenance for the larva once it hatches, confirming that the bee does not consume the wood itself. Newly emerged adults use the tunnels for overwintering and often expand the galleries the following spring.
Distinguishing Bee Damage from Other Insect Pests
Identifying the type of insect causing wood damage requires observing the visual evidence left behind. Carpenter bee damage is characterized by a nearly flawless, circular entrance hole, typically measuring about a half-inch across. This hole is the entryway to a long, clean gallery inside the wood.
Beneath an active hole, homeowners often find a pile of coarse sawdust, called frass, which is the material ejected during the bee’s excavation. Yellow or brownish streaks of fecal matter may also be visible on the wood surface near the entrance. In contrast, damage from termites is often hidden and results in wood that sounds hollow or has mud tubes on the surface, as they consume the wood from the inside out. Carpenter ants also create galleries, but their tunnels are irregular and smooth. Their frass contains insect parts and is coarser than the fine, powdery frass of subterranean termites.
Preventing Wood Damage to Structures
Protecting wooden structures from boring bees centers on making the wood unappealing for nesting. Carpenter bees strongly prefer soft, unfinished, or weathered wood. A highly effective preventative measure is ensuring all exposed wood surfaces are well-maintained with a coat of paint, varnish, or sealant. Applying a thick finish acts as a barrier that discourages the bee from attempting to bore into the surface.
Sealing and Deterrents
For existing holes, a crucial step is to wait until the current occupants have emerged, typically in late summer or fall, before sealing the entry. Filling the abandoned holes completely with wood putty, caulk, or a wooden dowel prevents the bees from reusing or expanding the tunnels. Certain natural deterrents, such as citrus oil or almond oil, can be applied to vulnerable wood surfaces, as the bees are repelled by these strong scents.