They are checking out my wooden deck.

Yes, the large black bees hovering around the outside of homes, buildings, sheds, barns and decks are carpenter bees.

They are searching for mates and favorable nesting sites. Meanwhile, female dogwood borers are looking for dogwood trees to lay their eggs. Memorial Day weekend is the time to manage this borer.

Male carpenter bees are quite aggressive, often hovering in front of people who are around their nests, according to Dr. Mike Potter, University of Kentucky Extension Entomologist.

However, males are harmless since they lack stingers. Females can inflict a painful sting but seldom will unless they are handled or bothered.

Carpenter bees resemble bumble bees, but the upper surface of their abdomen is bare and shiny black; bumble bees have a hairy abdomen with at least some yellow markings.

Despite their similar appearance, bumble bees usually nest in the ground, while carpenter bees usually tunnel into wood to lay their eggs. Carpenter bees prefer bare, unpainted, or weathered softwoods, especially redwood, cedar, cypress, and pine. Painted or pressure-treated wood is much less susceptible to attack. Common nesting sites include eaves, window trim, fascia boards, siding, wooden shakes, decks, and outdoor furniture.

Carpenter bees overwinter as adults in the wood. They emerge in spring, usually in April or May. After mating, the fertilized females excavate tunnels in wood and lay their eggs within a series of small cells.

The cells are provisioned with a ball of pollen on which the larvae feed, emerging as adults in late summer. The entrance hole and tunnels are perfectly round and about the diameter of your finger.

Coarse sawdust the color of fresh cut wood is often present beneath the entry hole, and burrowing sounds may be heard from within the wood. Female carpenter bees may excavate new tunnels for egg laying or enlarge and reuse old ones. The extent of damage to wood which has been used for nesting year after year may be considerable.

Carpenter bees prefer to attack wood which is bare, weathered, and unpainted. Therefore, the best way to deter the bees is to paint all exposed wood surfaces, especially those with a history of being attacked.

Wood stains and preservatives are less reliable than painting, but will provide some degree of repellency versus bare wood. To further discourage nesting, garages and outbuildings should be kept closed when carpenter bees are actively searching for nesting sites.

Managing the carpenter bee is best completed before tunnels are fully constructed. Liquid, aerosol, or dust insecticides with active ingredients such as bifenthrin, cyfluthrin, deltamethrin, or lambda cyhalothrin can be applied directly into tunnel openings. Read the label of the product.

Leave the hole open for a few days after treatment to allow the bees to contact and distribute the insecticide throughout the nest galleries. Plug the entrance hole with a piece of wooden dowel coated with carpenter’s glue, putty, or other suitable sealant to protect against future use of the nesting tunnels and to reduce the chance of wood decay.

The above mentioned insecticides may be used as a more extensive treatment on vulnerable wood surfaces when large numbers are attacking. Bees avoid drilling into the treated surfaces.

Apply the insecticide by using a pump-up or hose-end sprayer to target areas most favored by carpenter bees such as eaves, fascia boards, and joist ends of decks. Follow the label directions and precautions. Residual effectiveness of these insecticides is often only 3-4 weeks, so the treatment may need to be repeated.

Although carpenter bees are less aggressive than wasps, female bees taking care of their nests will sting. Treatment is best performed while wearing protective clothing or at night when the bees are less active.

When considering your dogwood tree, this week is the time to manage dogwood borers. The adult dogwood borer is a small, day-flying moth. It is blue-black with yellow bands and somewhat resembles a small wasp. The moth emerges and lays eggs, usually in May and June, near trunk wounds or in crevices in the bark.

Young trees are usually attacked near ground-level, often around lawn mower injuries. Infestation of older trees likely occurs in the limb crotches or on main limbs in association with pruning scars, cankers, or cracked bark.

Young borers hatch in one to two weeks and quickly tunnel into the tree. Once beneath the bark, borers are protected from insecticidal sprays and are seldom detected until serious damage has been done.

Early symptoms of trees attacked by borers are off-color foliage, wilting terminal shoots, and crown dieback. Large branches may die or become weakened and prone to wind breakage. Old trees may exist in an unthrifty condition and be re-infested year after year.

To protect dogwood trees from the dogwood borer, apply borer spray to runoff on the trunk and main scaffold limbs according to the label directions.

This will leave an insecticidal residue on the bark that will kill young borers as they hatch and attempt to bore into the tree. Active ingredients to look for in a borer spray are permethrin and bifenthrin. Make sure “ornamentals” are listed on the label and it controls borers. Only one treatment with the insecticide is recommended.

For more information, contact the Daviess County Cooperative Extension Service at 270-685-8480 and leave a message, or email

Annette’s Tip

Dr. Mike Potter, University of Kentucky Extension Entomologist, provides detailed information about the carpenter bee and its behavior at the website

Annette Meyer Heisdorffer is the Daviess County extension agent for horticulture. Her column runs weekly on the Home & Garden page in Lifestyle. Email her at


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