Bees are prized pollinators in the garden, but carpenter bees can become a springtime nuisance as they drill holes in wooden decks, windows, and eaves to raise their young. "Typically, carpenter bee holes don’t cause serious structural damage," says Ken Johnson, a horticulture educator with the University of Illinois Urbana-Champaign. "However, if the tunnels are used for several years, or multiple nests are excavated in the same piece of wood, it may compromise the structural integrity of the wood and allow moisture-causing decay to form."
Below, take a look at the common signs of an infestation, control methods (including how to get rid of carpenter bees naturally), and tips to prevent future damage.
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Common Signs of Carpenter Bee Infestation
According to Kerrie Roach, district specialist at Clemson University County Extension, "Homeowners often refer to these large, dark-colored insects as bumble bees because of their similarities in size and appearance." But carpenter bees have a shiny black abdomen and bumble bees have a hairy black and yellow abdomen. Bumble bees nest in the ground and carpenter bees excavate tunnels in wood that they return to each year unless steps are taken to prevent an infestation.
The first sign of a carpenter bee infestation is a perfectly round entrance hole (about 1/2 inch diameter) drilled by the female in untreated wood to lay her eggs that will hatch and mature over several weeks. You may first notice some sawdust before the hole is completed, but the bee can complete the drilling in just a couple of hours. Until the new generation of adult bees emerge, the male bee guards the hole aggressively against intruders. This might sound scary, but the good news is that the male bee has no stinger—the buzzing sound, however, can be a bit annoying. The female is not as aggressive as the male, but does have a stinger and knows how to use it.
How to Get Rid of Established Carpenter Bees
To get rid of an established carpenter bee infestation as soon as possible, experts recommend a liquid or dust commercial insecticide labeled for the control of wasps and bees. While plugging the hole may seem like a quick solution, if an insecticide is not used, the trapped adult carpenter bee can excavate a new opening. The best time for insecticide application is after dark when the bees are in the tunnels. Direct the product at the entrance hole to ensure good contact with the bees.
After at least twenty-four hours, use a caulking compound or wood putty to plug the hole. You can also coat a wooden dowel with wood glue and insert it into the hole. This will prevent other bees from using the tunnel and reduce moisture damage and wood decay, especially if you paint the wooden surface.
How to Get Rid of Carpenter Bees Naturally
If you don't like to use insecticides, a carpenter bee trap is helpful. You can purchase traps or build one yourself from raw, untreated wood. Most are a wooden box with 1/2-inch holes drilled on each side. A larger hole is drilled in the bottom so a glass or plastic bottle can be attached. The bees enter the holes and the light from the larger bottom hole draws them to the bottle where they become trapped. The bees can be relocated or allowed to die.
Another natural control method is to make or purchase a carpenter bee house filled with untreated pieces of wood. The house should be hung or mounted as far away from your home as possible to lure the bees. Once the bees discover the wood, they will return to it next year to lay their eggs instead of drilling into your deck.
How to Prevent Carpenter Bee Infestations
Carpenter bees are opportunists. They will use any holes in wood for nesting and if they don't find a hole, they will make one in untreated, raw wood. Follow these tips to prevent carpenter bee infestations:
- Plug all holes, seams, and gaps in wood structures with caulking or putty.
- Paint exposed wood with an oil or polyurethane-based paint. Wood stains do not repel carpenter bees.
- Use an insecticide additive in the paint to help repel bees, especially if you've had prior infestations.
- Use pressure-treated wood whenever possible for outdoor constructions.
- If wood has been severely damaged, replace it with a non-wood substitute, like composite, vinyl, or aluminum.
- Do not store firewood near untreated wooden structures, as this will attract carpenter bees.
- Prevent interior infestations by keeping doors and windows screened or closed during the early spring when the bees are actively searching for nesting sites.
