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Carpenter bees emerge this time of year

Posted: Sunday, April 04, 2010

They're back.


No, I'm not talking about the golfers and golf fans that flock to our area for The Masters. Most of us welcome these out-of-town guests for the week.

What I am talking about are some pests that show up this time every year. This past week, I saw my first carpenter bee.

Carpenter bees are large, black and yellow bees frequently seen in spring hovering around the eaves of a house or the underside of a deck or porch rail. They are most often mistaken for bumble bees, but differ in that they have a black, shiny tail section.

The carpenter bee is so-called because it excavates tunnels in wood with its strong jaws. The first sign of these bees is the pile of sawdust on the ground, patio or porch under a neat, half-inch hole that looks like it has been drilled into the wood.

These bees will drill into any type of wood, even wood that is supposed to resistant to insects, such as red cedar, cypress and redwood. They will even drill into some painted wood.

Carpenter bees overwinter as adults, often inside old nest tunnels. They emerge in late March through April with the males usually the first to appear. Males have a whitish spot on the front of the face. The males do not have stingers, but they are territorial and will harass other bees and people who venture near their protected areas. Females can sting, but rarely do so unless grabbed or made angry.

The bees feed on plant nectar, and then they begin constructing new tunnels in a few weeks.

When they make a tunnel, they will start on the underside of the piece of wood and the tunnel will move upward for a half-inch or more. Then the tunnel will turn and follow the wood grain. This is called a gallery. The female will lay six to seven eggs in a gallery.

These adult bees die after she has laid all of her eggs. The eggs hatch in a few days and the offspring complete their development in about five to seven weeks. Adults emerge in later summer. Although the bees remain active, feeding on pollen in the general area, they do not construct new tunnels. They can be seen cleaning out old tunnels that they will use as overwintering sites when the weather cools.

Carpenter bees do little structural damage to buildings, but the holes and sawdust they produce are unsightly. One of the problems that can be associated with carpenter bees is woodpeckers.

Woodpeckers have been known to attack the wood that has the carpenter bee larva in it. Also, there are wood decay organisms that can gain entrance through the hole made by the carpenter bee.

Preventing carpenter bee damage is difficult for several reasons. Protective insecticide sprays applied to wood surfaces are effective for only a short time. Because the bees are not actually eating the wood and they are active over several weeks, they are rarely exposed to lethal doses of the pesticide. Second, since virtually any exposed wood on the house could be attacked, it is difficult, usually impractical and unsafe to try applying a pesticide to all possible sites where the bees might tunnel.

Also, it is not wise to try spraying the bees while they are flying because of the possibility of being exposed to the pesticide. Treating the holes with an insecticide can reduce the use of the hole and possibly kill some of the bees. Products containing carbaryl (Sevin), cyfluthrin or resmethrin among other chemicals are suitable choices for controlling carpenter bees. The holes should be filled and sealed after.

Right now, there is another bee that is active -- the honey bee. They are swarming now. When honey bees fill up their hive or a pest such as mites become too bad, the bees will split and part of the hive will leave or the whole hive will leave. When this happens, it's possible to see a large ball of bees on a limb or other object. These bees will stay there until a new place is found to live -- for a few hours to a few days. Beekeepers will collect these bees and put them in hives.

Please don't kill these bees. Honey bee numbers are still dropping, and we need all the honey bees we can keep.

There are plenty of blooming plants right now, and honey bees and other bees are collecting pollen and nectar. When bees are away from their hive, they are non-aggressive. They are more interested in collecting pollen. Leave them alone.

If a swarm is spotted, contact me or the County Extension Office. We have a list of bee keepers who will come and collect the swarm.

Charles Phillips is a retired Columbia County Extension Service agent and operates Hort Consulting. He can be reached at


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