Carpenter bees are large, solitary insects often mistaken for bumblebees due to their size and yellow-and-black coloring. Homeowners are concerned about these bees because they bore into wood to create nests, raising questions about personal safety and property integrity. This article explores the risk of a bee sting and the potential for long-term damage to wooden structures.
Assessing the Risk to Human Health
The risk of being stung by a carpenter bee is often minimal. The ability to sting depends entirely on the bee’s sex. Male carpenter bees do not possess a stinger and are harmless to people, despite their aggressive-looking behavior. Males are often seen aggressively “dive-bombing” or hovering near nest sites, but this territorial display is purely a bluff used to deter intruders.
Female carpenter bees do have a stinger and can sting, but they are generally non-aggressive. They only sting if directly handled or severely provoked. The stings are typically less painful than those from a honeybee, and unlike honeybees, the female can sting multiple times. While usually mild, the sting can trigger a life-threatening allergic reaction in hypersensitive individuals, a risk associated with most bee and wasp stings.
Structural Damage to Wood and Property
The significant long-term danger posed by carpenter bees is cumulative damage to wooden structures. Female bees bore perfectly round, smooth-edged entrance holes, typically about a half-inch in diameter, into wood surfaces. They prefer unpainted, weathered, or softwoods (cedar, pine, cypress, and redwood), making decks, fascia boards, and eaves common targets.
Once inside, the female turns the tunnel at a right angle and excavates a gallery that runs with the wood grain, extending several inches to over a foot. The bees do not eat the wood; they chew it out to create a protected nest for their eggs. They use the sawdust-like waste, called frass, to separate individual brood cells. A single nest usually poses little threat to structural integrity. However, the problem compounds because generations of bees often return to the same location, expanding old tunnels or drilling new ones nearby.
Over many years, this repeated activity can weaken wood by removing a percentage of a beam’s cross-section. Furthermore, open tunnels allow moisture to infiltrate the wood, accelerating fungal decay and wood rot. This decay causes more severe damage than the bees’ tunneling alone. Woodpeckers are also attracted to the wood, chiseling the surface to feed on the bee larvae inside the galleries, turning a small hole into a much larger gouge.
Distinguishing Carpenter Bees from Bumblebees
Carpenter bees are frequently misidentified as bumblebees due to their similar size and coloring. The clearest visual distinction lies in the abdomen. Carpenter bees have a shiny, black, and hairless abdomen that often looks polished or metallic.
In contrast, bumblebees are covered in dense, fuzzy hair across their entire body, including the abdomen, giving them a more robust, teddy-bear-like appearance. Behaviorally, the species differ in their nesting habits. Carpenter bees are solitary nesters, with a single female creating her own nest in wood. Bumblebees are social insects that live in colonies with a queen and workers, typically nesting underground in old rodent burrows or dense grass.
Options for Managing Nesting Activity
Homeowners should focus on remediation of existing damage and prevention of future nests. For active holes, apply an insecticidal dust directly into the entrance, preferably at dusk when the bees are inside. Do not seal the hole immediately. Instead, wait several days to two weeks after treatment to ensure all adult bees have been exposed to the insecticide.
Once the nest is confirmed inactive, the hole can be plugged with wood putty, a wooden dowel, or caulk, and then painted or stained. Preventing future activity is most effective through wood treatment, as carpenter bees strongly prefer bare, unpainted, or unstained wood. Applying a fresh coat of paint or varnish to exposed wood surfaces creates a deterrent barrier that significantly reduces new nesting attempts. For severe or hard-to-reach infestations, particularly those causing significant structural concern, consulting a pest control professional is recommended.