For Release June 17, 2003

Carpenter Bees "Wood" Be Trouble If Left Unchecked

AGRI-VIEWS
by Chuck Otte, Geary County Extension Agent

When is a bumble bee not a bumble bee? The answer is when it's really a carpenter bee. Carpenter bees, also known as wood bees, are very active right now. The numbers of carpenter bees seems to be up quite a bit in recent years as well. While the damage they do in any one year often isn't too bad, several years of activity can weaken wood to the point where repairs are needed.

Carpenter bees look a lot like bumble bees except that the top of the abdomen, the back body part, is shiny black and almost bare of hairs where a bumble bee's abdomen is yellowish and hairy. Carpenter bee females excavate perfectly round holes, about 3/8 to ½ inch in diameter. Since they do not actually eat the wood, you can often be tipped off to problems by the presence of sawdust. Carpenter bees are solitary nesters. Only one female will be active at any one hole, but several females may have nest tunnels in the same area or even in the same board.

From April to June the females mate, excavate burrows and then pack them with eggs and bee bread, a mixture of pollen and regurgitated nectar. This bee bread serves as food for the larva when it hatches. These larvae will feed, grow and pupate over the next one to three months. They will then emerge in late August but won't mate and start nexting until next spring. As it is with any bees, all the work is done by the female. Males hang around where females are active. They hover like hummingbirds in front of the tunnels waiting for an opportunity to mate with one of the females.

Once the tunnel is completed and all the eggs laid, the males and females disperse and spend the rest of the summer loitering nearby or feeding at flowers. If the males are disturbed they will fly and hover around your head, often making many threatening passes at you. Males can not sting. Only females sting and then only if really harassed.

Carpenter bees will usually only excavate into wood that is unpainted, and then usually only in sheltered areas, such as the underside of decks. One good prevention technique is to paint the underside of your deck with a dark paint, even a redwood colored paint. This will reduce the chance of carpenter bees moving in. Pressure treated wood is seldom attacked and is a good alternative to painting.

For existing infestations you can treat with a wasp and hornet killer or the insecticide Sevin. Sevin works best if you can find 5% or 10% dusting powder and inject it into the nest holes. It is best to do this in the evening when there is less bee activity and also a better time to catch the female in the tunnel. Do not plug the holes right away. You want the carpenter bees to continue coming and going to increase the chance of coming in contact with the chemical control. The holes can then be filled this fall.

Males are the most frightening to people because they are the most visible. Using an aerosol wasp and hornet spray to knock these offenders down is probably the best approach. While it is very uncommon for a female carpenter bee to sting, it can happen. If you know, or suspect that you may be allergic to bee stings, do not attempt any bee control, of any kind, by yourself. Have someone else do it.

This is a banner year for carpenter bees. While seldom a threat to your safety, they can be a threat to your untreated wood if left unchecked for several years. It is better to get them under control now!

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