Ride: carpenter bees on patrol


Carpenter bees have been very active in the past few weeks. Local residents alerted the office because these large bees are flying near eaves. Here are a few facts about carpenter bees that you may not know about.

Very often it is the male carpenter bee that patrols the area. The male carpenter bees cannot sting and the females are not aggressive but can bite and sting if handled. Males can be easily distinguished from females by their white markings on their faces.

Carpenter bees are large bees and resemble bumblebees in appearance, except that the dorsal (upper) surface of the abdomen is almost hairless and appears completely black in the carpenter bee. Don’t confuse the white-faced male carpenter bee with a bald hornet who also has a white face. If your misfortune leads you to encounter a female bald-headed hornet, you will realize that she is not forgiving.

While carpentry bees are pollinators for several species of plants, they are considered pests when they dig into wood. A breeding gallery is excavated in weathered and mostly unpainted wood, and the exit hole is a near-perfect circular hole about 1/2 inch in diameter. These holes often look like they were made by a drill. The gallery initially extends straight out of the opening, but soon makes a right-angled turn to follow the grain of the wood. The female lays an egg in the gallery, supplies it with nectar and pollen and seals the cell with chewed wood pulp. Galleries can contain six cells and average four to six inches long. However, because galleries are reused and can be used by more than one bee, tunnels up to 3 meters in length have been reported. The new adults will appear in late summer.

Non-chemical or preventive controls include painting or varnishing wooden surfaces. Individual bees can be caught with a net and killed or hit with a badminton racket (if anyone else has one). Also, a flexible wire can be inserted into the hole to kill adult bees and larvae, but the wire must be strong enough to break through the wood cells and flexible enough to rotate at the correct angle.

Insecticidal dusts can be blown into nest holes in the evening when the house bees are resting. Insecticidal dust fills the cavity very well and does not penetrate the wood like a liquid. The bees should have 24 hour access to the nest so that they can distribute the dust in the galleries. After this time, seal the hole with putty, a wooden dowel or cork to prevent re-infestation. Carpenters bees overwinter in tunnels that are already in use, so the building should also be inspected in autumn and any holes that may have occurred should be treated and sealed.

Of course, I would encourage you to scare off the bees rather than kill them, but often the damage becomes too severe and requires insecticides. If using insecticides, read and follow all directions for use on the label.

Hopefully you can avoid structural problems in carpenter bees without using pesticides. It takes some time to fill the holes, but the pursuit of being bee-friendly can make a difference in our bee population. If you have any questions about carpenter bees, call the Henderson County Extension Office; we are happy to help!

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