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Carpenter bee pollinating a flower

AUBURN UNIVERSITY, Ala. – Carpenter bees have emerged in Alabama, sending property owners into defense mode. These extra-large pollinators may seem intimidating. Unfortunately, they are intimidating because their primary intention is to move into your home.

Carpenter Bees

In Alabama, the most common species of carpenter bee is Xylocopa virginica. Adult carpenter bees—male and female—spend winter hibernating inside old nest tunnels. Overwintered adult bees emerge in early spring to mate and search for new nest sites.

These bees earn their name because of their natural tendency to bore one-half-inch holes that appear to be perfectly round on exterior wood surfaces. These bees remain active through the summer.

Carpenter bees are good pollinators, and naturally nest in dead trees and wood piles. However, they live in close proximity to humans and can cause extensive damage to wood structures. The pollinators can potentially affect homes, especially when they repeatedly colonize in exposed wood without control.

Uninvited Guests

“Female carpenter bees are the ones causing the damage,” said Alabama Cooperative Extension System Entomologist Xing Ping Hu. “To lay eggs, females drill into dry wood on home features such as siding, fascia boards, porch window trim, porch ceilings, fence, decks, outdoor furniture and other wooden surfaces.”

The female bee chews a perfectly-round entrance, about the size of a dime, directly into wood. These entrances are typically an inch in depth, then make a turn at a 90-degree angle to excavate a gallery. Galleries usually follow the grain of the wood. Inside each gallery, females construct six to 14 cells. In each cell are privations of mixed pollen and nectar balls. Eggs are placed on the balls and cells are sealed off shortly after with chewed wood pulp. After hatching, larvae will develop into adults and will chew through the cell partition and emerge in late summer.

Signs of Carpenter Bee Infestation

There are several signs that property has become a breeding site for carpenter bees. Look for the following signs when surveying home and yard areas:

  • Carpenter bees hover nearby and around your building and structures—they are looking for nesting sites
  • Coarse sawdust that collects beneath excavated cavities during the spring
  • Round and smooth holes in size of a dime on exterior wood surfaces
  • Unsightly stains caused by falling bee waste around the circular entrance hole
  • Noticing a buzzing or burrowing sound coming from within the wood

Do carpenter bees sting?

Hu said carpenter bees are highly unlikely to sting people. Females have a stinger, but are not defensive unless directly provoked. Bees hovering nearby or buzzing around people after approach are most likely males that are putting on a territorial show of aggression. Don’t worry; males do not have a stinger, making them harmless. If an individual gets close enough to tell, males have a white or yellow blaze on their face while females have a dark face.

A Mistaken Identity

A close family member of the carpenter bee is the bumble bee. Known for their stinging capability and similar color pattern, bumble bees are often mistaken for their larger cousins.

“An easy way to tell these two apart is by looking at their abdomens,” Hu said. “The abdomen of carpenter bee is shiny, black and hairless. The bumble bee is covered with soft, fuzzy hairs patterned with distinct black and yellow stripes.”

These two species also behave differently. Below are some contrast traits of each insect.

  • Carpenter bees are solitary bees, less defensive of their nest sites. Bumble bees are social and extremely defensive when their nest site is disturbed.
  • Carpenter bees tend to stick closely to their preferred wooden environment. Bumble bees are likely found around blossoming plants and flowers.
  • Carpenter bees fly in a more erratic way. It may appear like carpenter bees are chasing one another rather than flying together in harmony, while bumble bees fly leisurely together.
  • Carpenter bees carve their own tunnels and nest in above-ground wood materials. Bumble bees live in social colonies, usually nesting in the ground.

Carpenter Bee Control

When to Act

Early spring is the best time to treat and prevent carpenter bees. Openings on wood surfaces must be sealed in order for bees to be deterred.

Timing is also important because the goal of carpenter bee control is to avoid the nesting damage. However, people shouldn’t eliminate all of the bees in the yard since they are important pollinators. The best time to intervene is before the females lay eggs in their tunnels. Products with essential oil components can deter carpenter bees from carving tunnels or abandoning the excavated nest.

What to Do

A painted surface is also a deterrent to carpenter bee activities. Unfortunately, painting or placing polyurethane on wood decks or log homes is often not a desirable option. Wood stains also provide little repellant.

If practical, severely damaged wood should be removed and replaced with chemical pressure-treated wood to prevent nest construction. Consider use of synthetic sidings rather than wood sidings. Sometimes, it is necessary to control carpenter bees that are causing damage. Simply sealing the entrance holes with caulking or expanding foam does not work if the holes are not treated with a pesticide.

The trapped adult carpenter bees can chew through caulk, escaping or excavating new openings. Commercial and homemade traps can catch carpenter bees if properly installed, but often do not provide effective control around a structure.

Insecticide Pros and Cons

There are insecticide products commercially labeled for carpenter bee control. They can be applied to exposed wood and gallery entrances. These products are formulated for dusting, aerosol, foaming and liquid sprays.

Each formula has its pros and cons. Sprays can be the easiest to apply, but too much spray may soak the raw wood. Aerosol sprays, especially foaming formulations with a straw attachment, can be effective if applied to each hole. However, overuse can soak the chemical into raw wood over time. Dusts applied to each hole will stay on the surface and can be effective, but dusts can be messy to apply without a specially-made applicator.

“Whatever the product used, all label directions must be followed,” Hu said.

Applications should be late in the evening when the female bees are most likely to be inside the wood tunnels and less active. Additionally, it is always a good idea to wear a long-sleeved shirt, chemically resistant gloves and protective eyewear when making applications. This step can reduce the chances of being stung.

After applying an insecticide, people should plug the tunnel entrances using trebor plugs, super plugs or wood patch material to stop other insects from invading the holes at a later time.

More Information

To learn more about carpenter bees and their habits, visit the Alabama Extension website at www.aces.edu.

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