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CARPENTER BEES
By: Stephen B. Bambara and Michael Waldvogel, Entomology Extension |
Insect Note
- ENT/rsc-4
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 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 of its habit
of excavating tunnels in wood with its strong jaws. The round
half-inch diameter entrance holes are usually found on the underside
of a board. A tell-tale trace of coarse sawdust is often found on the surface
beneath the hole. Wooden decks, overhangs and
other exposed wood on houses are prime targets. Painted and treated woods are less preferred, but they are by no means immune to attack.
Unpainted or stained cedar, cypress and redwood shingles and siding are also attacked despite their pest-resistant reputations. Carpenter bees, like their distant relatives, the carpenter ants, differ from termites in that they do not eat the wood as food. They simply excavate tunnels for nesting sites. |
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DAMAGE Like most other bees, female carpenter bees are capable of stinging. However, unlike the "social bees" such as honey bees and bumble bees, carpenter bees do not have workers which defend the nest. Therefore, carpenter bees rarely sting. CONTROLPreventing carpenter bee damage is difficult (or nearly impossible) for several reasons. Protective insecticide sprays applied to wood surfaces are effective for only a short period even when repeated every few weeks. Since 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 and usually impractical and unsafe to try applying a pesticide to all possible sites where the bees might tunnel. Trying to spray bees that are seen hovering about is not a sensible (or particularly safe) use of pesticides either. Swatting hovering bees will often prove to be just as effective. Although it is a time-consuming and seemingly endless task, treating the entrance holes with an insecticidal spray or dust can reduce future nesting activity. Products containing carbaryl (Sevin), cyfluthrin or resmethrin among other chemicals are suitable. A list of chemicals for use against carpenter bees can be found in the NC Agricultural Chemicals Manual . Avoid inhaling the insecticide or contaminating your clothing with the spray. Always stand upwind from the surface you are treating. Active or abandoned tunnels may be used as overwintering sites or can be re-used next spring for making a new nest. You should seal the treated tunnels with a small ball of aluminum foil and then caulk them after 24-36 hours. The insecticide treatment is important because it kills both the adult bee as well as any offspring as they attempt to emerge later. Simply plugging untreated tunnels with wire mesh or similar material might trap bees inside, but more resourceful bees will simply chew another exit hole. Another option for preventing carpenter bee damage is to use non-wood trim and siding products, such as fiber cement or composite siding and/or trim, although some people find this aesthetically and economically undesirable. |
| Image of Carpenter bee on a flower - J.K. Barnes, U. of. Ark |
Pest information and control recommendations presented here were developed for North Carolina and may not be appropriate for other states or regions. Any recommendations for the use of chemicals are included solely as a convenience to the reader and do not imply that insecticides are necessarily the sole or most appropriate method of control. Any mention of brand names or listing of commercial products or services in the publication does not imply endorsements by North Carolina Cooperative Extension nor discrimination against similar products or services. All recommendations for pesticide use were legal at the time of publication, but the status of pesticide registrations and use patterns are subject to change by actions of state and federal regulatory agencies. Individuals who use chemicals are responsible for using these products according to the regulations in their state and to the guidelines on the product label. Before applying any chemical, always obtain current information about its use and read the product label carefully. For assistance, contact the Cooperative Extension Center in your county. Distributed in furtherance of the acts of Congress of May 8 and June 30, 1914. North Carolina State University and North Carolina A&T State University commit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age, or disability. In addition, the two Universities welcome all persons without regard to sexual orientation. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating. |
Carpenter bees overwinter as adults, often inside old nest tunnels. They
emerge in April and May with the males usually the first to appear. Males
can be distinguished from females by 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 confined in your hand or are highly
agitated. They feed on plant nectar, then begin constructing new tunnels
in a few weeks. The 
Typically, carpenter bees do
not cause serious structural damage to wood unless large numbers of bees
are allowed to drill many tunnels over successive years. The bees often
eliminate their wastes before entering the tunnel. Yellowish-brown staining
from voided fecal matter may be visible on the wood beneath the hole as seen in the picture above.