Carpenters bees are on patrol, but steps can be taken to control them

Carpenter bees have started to be very active in the past few weeks, and local residents are alarmed by these large bees flying near eaves or on porch overhangs.

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 are easy to distinguish from females by their white markings on their faces if you dare to get close enough to see them.

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-headed hornet, who also has a white face. You will most likely encounter a female bald-headed hornet, and she is not forgiving.

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While carpentry bees are pollinators for several plant species, including maipops, 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. In the gallery the female lays an egg, 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 re-used and can be used by more than one bee, tunnels up to three 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 and killed with a net or hit with a badminton racket. 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 indoor 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 spread the dust in the galleries. After this time, seal the hole with putty, a wooden dowel or cork to prevent re-infestation.

Carpenter bees overwinter in previously used tunnels, so the building should also be inspected in autumn and any holes that may have been treated and sealed.

There really is no such thing as quick, magical controls for carpenter bees, but with a little patience you can reduce their numbers significantly. If you have any questions about carpenter bees, call the Henderson County Extension Office; we are happy to help!

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