Hello,

Thank you for sending photos. From your description and photos these insects are likely carpenter bees. To confirm the identification further you can use the following carpenter bee traits:

• Eastern carpenter bees are large bees approximately 0.75-1 inch long.
• The thorax or midsection is covered with yellow fuzz. The abdomen, or the hind section, is shiny and black and mostly hairless.

Carpenter bees are native solitary bees. Each female builds her own nest by tunneling into wood. These tunnels, along with other materials, form cells where the bees lay their eggs to rear their young. This type of tunneling does wear on the wood and can also attract other animals like woodpeckers that are looking to eat carpenter bee larvae and other insects within the wood. Each tunnel typically extends 6-12 inches long but if tunnels are reused year after year by new carpenter bees the tunnels can get up to 10 feet long. A female bee often lays her eggs in the same gallery in which she developed.

Carpenter bees are attracted to raw, unfinished softwood (especially cedar, redwood, and clear pines). Nail holes, splinters, and cracks within the wood can also be attractive. For treating and repairing the wood and tunnels it is generally recommended to apply a pesticide (wasp, hornet, or bee aerosol formulation) within the tunnels (killing any immature bees inside) before caulking. Apply the aerosol material into the tunnel entrances and along exposed surfaces. There are also insecticide dust formulations labeled for carpenter bee control. Dust is effective when small amounts are puffed into the tunnel. Chemicals are often repellent to the bees in large quantities so the objective is to lightly treat the inside of the tunnel entrances. Read and follow all chemical label directions.

If you suspect there are still bee in the tunnels, you could wait for them to emerge before applying a pesticide. Carpenter bees are not aggressive and do not defend their nests but if they are inside the tunnels, they will try to burrow their way out during any chemical applications. Wait about a week after applying pesticides and look to see if there is any new activity. If the tunnels appear inactive, you can then caulk the tunnels and entrance holes. After caulking, painting and sealing the wood can help deter future wood boring damage.

If these tunnels are in a hard to reach area, a professional pest control company can be hired. Most companies provide free estimates, at which time they discuss a treatment plan and cost. Companies should fully disclose information on the chemical that they will be using in the treatment. Companies that are members of the Maryland Pest Control Association and the National Pest Management Association have access to all current treatment practices. You can check a company's reputation by calling the Better Business Bureau. Make certain that the company has an active certification license from the Maryland Department of Agriculture Pesticide Regulation Section. A professional pest control company could also help to assess any structural damage and let you know if another professional needs to be brought in. Tunneling from a single carpenter bee typically does not cause major structural damage, but if there are tunnels from multiple bees, that may have been reused over years, the wood may be weakened. Secondary damage as a result of the tunnels could include moisture build up, wood decay, mold growth, and woodpecker damage.

Carpenter bees are important pollinators, so if you find any that have emerged you could try to encourage them outside as that is where they want to be (they are only inside your house by accident). In natural environments they would emerge outside from their wood chambers ("nests"). A sustainable method of deterring carpenter bees from nesting in areas where we do not want them is to provide alternative nesting sites. To do this, one can use pieces of wood that one may not be interested in keeping (such as old, already nested in wood), and displaying them in other parts of the open spaces so that females choose to nest in those surfaces instead of in the wood we want to protect. Besides protecting the wood, this also allows us to support these important native pollinators from our region, all while reducing the potential negative impacts on our buildings. Some carpenter bees also utilize plant materials like hollow reeds or pithy plant stems for nesting; adding this plant material (wildflowers like stiff goldenrod [Solidago rigida], raspberry canes [Rubus spp.], and/or Yucca spp.) to your landscape can provide them alternative nesting sites, deterring them from your buildings. For more information on providing alternative nesting sites for beneficial bees and pollinators, please see this Xerces Society guide: https://xerces.org/publications/fact-sheets/nesting-overwintering-habitat. For more information on carpenter bees, please visit this UMD Extension webpage : https://extension.umd.edu/resource/carpenter-bees/.