Carpenter bees are solitary structural pests that drill into wooden structures to create nests. The female bee excavates tunnels in wood to lay her eggs. Their presence can cause noticeable damage over time, requiring swift action. This guide provides practical steps for removing an active infestation and protecting your property from future activity.
Identification and Nesting Habits
Correct identification is the first step toward effective control, as carpenter bees are often mistaken for bumblebees. The most reliable way to distinguish them is by looking at the abdomen. A carpenter bee has a shiny, black, and hairless abdomen. In contrast, a bumblebee’s abdomen is covered in dense, fuzzy hair with yellow and black markings.
The telltale sign of an infestation is the perfectly round entry hole, typically about a half-inch in diameter. The female bee bores into the wood, excavating it to create a gallery for her offspring without eating the wood. This process leaves behind coarse sawdust, known as frass, which often piles up directly beneath the entrance hole.
After drilling through the surface, the female turns sharply, excavating a tunnel parallel to the wood grain that can extend several inches or feet. Within this gallery, she partitions individual chambers with wood pulp and pollen, laying a single egg in each. Adult carpenter bees emerge in the late summer or fall. They often reuse or expand existing tunnels the following spring, causing damage to accumulate over multiple seasons.
Immediate Treatment Methods
The most effective approach for eliminating an active infestation is applying an insecticide directly into the nesting tunnels. Insecticide dusts are the preferred treatment because they distribute easily and reach deep into the gallery system, affecting both bees and developing larvae. Effective products contain active ingredients like carbaryl, permethrin, or deltamethrin. Apply the dust into the circular entry holes using a hand duster tool.
Perform this application in the late evening or early morning when the bees are most likely to be inside the tunnels. Leave the holes open for several days, allowing the bees to move through the insecticide dust. Adult bees will track the dust through the tunnels, contaminating the nesting site and ensuring emerging adults or larvae contact the treatment.
For immediate control of flying adults, use a contact aerosol spray, especially for bees hovering aggressively around the wood. Surface sprays, however, offer only temporary relief and do not reach protected larvae deep within the galleries. Specialized carpenter bee traps can also be used as a non-chemical supplement. These traps lure foraging adults into a collection chamber and should be placed near affected areas to intercept bees searching for nesting sites.
Repairing Damage and Long-Term Prevention
After the active infestation is treated, secure the damaged wood and implement measures to prevent future bee activity. Timing is important: the treated holes must remain open for one to two weeks after insecticide application. This ensures all bees and larvae have been eliminated or contacted the residual material. Sealing the holes too soon can trap living bees, forcing them to chew a new exit hole and potentially expanding the damage.
Once the tunnels are confirmed inactive, seal the holes with a durable material to prevent re-entry and moisture intrusion. Use wood putty, wood filler, or a glue-coated wooden dowel rod driven into the hole and sanded flush. For a robust seal, professionals often recommend using steel wool or metallic mesh as a plug before covering it with caulk or putty, since bees cannot chew through metal.
Long-term prevention focuses on making the wood surface undesirable, as bees strongly prefer untreated, unpainted, or weathered wood. Applying a protective coating like oil-based paint, stain, or polyurethane varnish creates a hard, slick barrier that deters drilling. Regular maintenance of these finishes, especially on exposed wood like fascia boards, eaves, and deck railings, is the most reliable defense against carpenter bee damage.
When Professional Intervention is Necessary
While many infestations are manageable with DIY methods, certain situations require a pest control professional’s specialized knowledge and equipment. A primary concern is an infestation unchecked for multiple seasons, leading to extensive tunnel systems that compromise structural integrity. If bees are boring into load-bearing elements, such as roof rafters or support beams, the damage may require structural repair beyond simple sealing.
Inaccessible nesting sites also warrant professional assistance, especially when entry holes are high off the ground, deep inside walls, or within hard-to-reach eaves. Professionals have access to commercial-grade insecticides and specialized tools to treat these difficult areas effectively and safely. They can also perform a thorough inspection to determine the full extent of the infestation, including hidden galleries. Recurring infestations, where bees return yearly despite consistent treatment, often require the comprehensive, long-term preventative applications that experts provide.