Carpenter bees have been very active the last few weeks and residents have been calling alarmed by these large bees flying near eaves. Quite often it is the male carpenter bee that is seen patrolling the area. The male carpenter bee is unable to sting and the females are not aggressive, but may bite and sting if handled. Males are easily distinguished from females by their white marking on their face.
Carpenter bees are large bees and similar in appearance to bumble bees, except the dorsal (top) surface of the abdomen is almost devoid of hairs and appears to be entirely black in the carpenter bee. Do not confuse the white-faced male carpenter bee with a bald-faced hornet which also has a white face. You are most likely to encounter a female bald-faced hornet and she is not forgiving.
While carpenter bees are pollinators for several species of plants including maypops, they are considered pests when they bore into wood. A gallery for brood is excavated in weathered and usually unpainted wood and the exit hole is a nearly perfect circular hole about 1/2 inch diameter. These holes often appear as if they were made by a drill bit. The gallery initially extends straight from the opening, but soon makes a right angle turn to follow the grain of the wood. In the gallery, the female lays an egg, provisions it with nectar and pollen, and seals the cell with chewed wood pulp. Galleries may contain six cells and average four to six inches long. However, because galleries are reused and may be used by more than one bee, tunnels up to 10 feet have been reported. The new adults will emerge in late summer.
Non-chemical or preventive controls include painting or varnishing wood surfaces. Individual bees can be caught with a net and killed or swatted with a badminton racket. Also, a flexible wire can be inserted into the hole to kill adult and larval bees, but the wire needs to be strong enough to break the wooden cells and flexible enough to make the right angle turn.
Insecticidal dusts can be puffed into nest holes in the evening when the carpenter bees are at rest. Insecticidal dust fills the void very well and will not soak into the wood as a liquid might. The bees should have access to the nest for 24 hours to allow them to spread the dust through the galleries. After this time period, seal the hole with putty, a wooden dowel, or cork to prevent re-infestation. Carpenter bees overwinter in previously used galleries, so the structure should also be inspected in the fall and any holes that may have formed should be treated and sealed.
Kelly R. Jackson is the Christian County Extension Agent for horticulture. He can be reached at 270-886-6328 or visit Christian County Horticulture online at www.christiancountyextension.com.