Wednesday, August 12, 2009

Destructive Carpenter Bees

Carpenter bees are 3/4 to 1 inch in length and resemble bumble bees, except that their abdomen is hairless and shiny black rather than being covered by patches of yellow-orange hair that is found on bumble bees. Adult carpenter bees become active in April or May and the female carpenter bees can sting, but usually only if agitated. Although males are incapable of stinging, they are territorial and will “attack" people passing by their nesting sites.
After mating, the females construct new nesting tunnels or use pre-existing tunnels for their nest site. Carpenter bees can bore holes about ½ inches wide into wood overhangs, decks, fence posts and trees. Unfinished wood or wood that is well weathered, poorly painted or stained is preferred for nest construction. Their nesting tunnels tend to extend straight for an inch or two and then turn 90 degrees as it begins to follow the wood grain. Their tunnels are clean cut and may extend 6 to 8 inches. Carpenter bees do not consume wood, but use wood merely to construct nests. Damage by carpenter bees is largely cosmetic, unless nesting sites are used repeatedly over years.

Some Control Options
Some Non-Chemical Control Options:Carpenter bees prefer to nest in unfinished or weathered wood, so painting or staining all exposed wood surface will deter carpenter bees from tunneling. Another option for preventing carpenter bee tunneling is to use non-wood trim and siding products, such as fiber cement or composite siding.

Some Chemical Control Options:
Observing bee activity will help in identifying nesting entrance holes. Look for perfectly round holes, about the size of a dime. Treating the entrance holes with an insecticidal spray or dust can reduce future nesting activity. Such products that contain carbaryl, cyfluthrin, permethrin, or resmethrin can be used. Leave the treated hole open for 12 to 24 hours before plugging it. The insecticide treatment is important, since it kills both the adult bees and offspring as they attempt to emerge later. Treatment is best performed at night when the bees are less active, or while wearing protective clothing.

A carpenter bee, Xylocopa sp. (Hymenoptera: Xylocopidae), nest opening. Photo by G. McIlveen, Jr.

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