Things You'll Need
Insecticidal dust or spray
Wood filler or wooden dowel and carpenter's glue
Carpenter bees are large, fuzzy bees that bore holes in unfinished wood to nest and lay eggs. The male bees then guard the nest, often harassing people in the process. However, carpenter bees rarely sting because the males have no stingers and the females are docile. Carpenter bees are beneficial because they help pollination, but they can become a problem when they damage building materials, such as decks, siding and eaves. You can stop carpenter bees from boring holes in your deck using several methods.
Spray the entrance to the carpenter bee tunnel with an insecticidal spray labeled for use against wasps, hornets and bees. You can use a product that contains carbaryl, chlorpyrifos or a synthetic pyrethroid. Alternatively, puff an insecticidal dust that contains carbaryl, bendiocarb or diazinon as the active ingredient into the tunnel. Let the insecticide work to kill all the carpenter bees for one to two weeks.
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Seal the tunnel hole of the carpenter bees with a wooden dowel covered with carpenter's glue or wood putty. You can get these materials from a home improvement store. Sealing the hole prevents other carpenter bees from using the old nesting tunnels and protects the wood against decay.
Paint or seal exposed wood in your deck to prevent other carpenter bees from coming and establishing their nest in your deck. Carpenter bees only bore unfinished wood, so painting or sealing your deck keeps them away. The Michigan State University Extension recommends using oil-based paint as it is the most effective material to protect a deck from carpenter bees. You can also use polyurethane, latex-based paints, wood stains and preservatives, but they tend to be less effective.
Wear protective clothing to minimize stings when you are working with carpenter bees because female bees may sting when threatened. Apply carpenter bee treatment at night when bees are less active.
Don't treat a carpenter bee nest yourself if you are allergic to insect stings. Instead, get another person to help you or call a pest control company.