Carpenter bees are a common pest that can compromise the structural integrity of wooden elements around a home. Unlike honeybees, these insects do not consume wood. Instead, they bore perfectly round, half-inch diameter holes to excavate tunnels for nesting and laying eggs. This tunneling behavior often targets fascia boards, eaves, and decks, weakening wood and attracting secondary pests. Homeowners should implement effective, non-toxic deterrents to encourage the bees to nest elsewhere.
Repelling Carpenter Bees with Scents and Oils
Carpenter bees are highly sensitive to strong odors, which interfere with their ability to locate suitable wood for nesting. Aromatic substances, particularly essential oils, function as natural repellents by creating an unappealing sensory environment. Citrus scents, such as lemon, orange, and citronella, are highly effective deterrents because the bees actively avoid the intense fragrance.
Specific essential oils, including lavender, peppermint, tea tree, and eucalyptus, can be combined with water and sprayed onto vulnerable wooden surfaces. The menthol scent of peppermint is overwhelming to the bees, while the medicinal aroma of eucalyptus is equally disliked. Since these volatile oils quickly dissipate, reapplication every few days is necessary to maintain a consistent sensory barrier.
Almond oil or extract is another specific repellent, containing the compound benzaldehyde. Benzaldehyde is a naturally occurring aromatic compound that disrupts the bee’s chemoreceptors, making the wood undesirable for nesting. This oil can be poured directly into existing holes or sprayed onto affected areas. It offers a longer residual effect, sometimes lasting for several months.
Making Wood Surfaces Unappealing
Female carpenter bees actively seek out soft, unfinished, or weathered wood because it requires less effort to drill and excavate tunnels. The simplest deterrent is to eliminate the bare wood surfaces that the bees naturally prefer. Applying a finish creates a hard, slick barrier that is difficult for the bee’s mandibles to penetrate.
Paint is an effective surface treatment because the bees often do not recognize a fully painted surface as wood. Multiple coats of a quality paint or a polyurethane gloss topcoat are recommended to create the hardest possible surface layer. While wood stains are less reliable than paint, they are better than leaving wood bare, especially when paired with a protective topcoat.
For structural areas like rafters, eaves, or deck joists that are frequently attacked, a more permanent physical barrier may be necessary. Covering vulnerable wood with aluminum flashing, vinyl siding, or other metal sheeting completely prevents the bee from accessing the surface. This ensures the bee cannot bore into the material regardless of its hardness or finish.
Exclusion and Damage Mitigation
Preventing carpenter bees from returning often requires mitigating damage in locations where they have previously nested. Female bees often return to or expand existing tunnels, making it necessary to seal any holes left from previous generations. Sealing should only occur after any adult bees have left the area, usually in late summer or fall, to prevent them from drilling new escape holes.
The most common way to seal an old nest entrance is by using wood putty, wood filler, or a tightly fitted wooden dowel. Using a wooden dowel or cork ensures the seal is flush and provides a solid surface that can then be painted or stained. This repair stops the area from attracting new bees seeking an easy, pre-excavated tunnel to reuse.
When replacing or building new wooden structures, choosing materials that are inherently less attractive to the bees provides a long-term solution. Carpenter bees prefer softwoods like pine, cedar, and cypress, which are easy to excavate. Hardwoods, such as oak, maple, and dense pressure-treated lumber, are less susceptible to attack because their dense fibers require greater effort to penetrate.