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Carpenter bees sometimes become a nuisance outdoors when they fly
very erratically (hover) around the heads of people, causing fear.
Homeowners complain not only about the aggressive nature, but about
the round holes bored into wood trim near eaves and gables of homes,
facia boards, porch ceilings, outdoor wooden furniture, decks,
railings, fence posts, telephone poles, siding, shingles, dead tree
limbs and other weathered wood. Initial damage is minor, but new
tunnels may be excavated and old ones enlarged, causing considerable
wood damage. Also, the yellow, coarse sawdust from borings beneath
their entry hole contain their waste materials, leaving unsightly
stains.
Identification
Carpenter bees resemble bumble bees. They are large, 3/4 to 1 inch
long, heavy-bodied, blue-black to black colored with a green or
purplish metallic sheen. The thorax is covered with bright yellow,
orange or white hairs and the abdomen, especially on the top side, is
black, shiny and bare without hairs. It is the males, with white
markings on their head, that fly around aggressively, but they are
harmless since they lack a stinger. Females have black heads, are
docile and rarely sting. They have a dense brush of hairs on the hind
legs whereas bumble bees have large pollen baskets and numerous,
yellow hairs on the abdomen. Larvae are saclike, white and legless
with brown, globular heads that bear small mouthparts. The pupal stage
is passed in a silent cocoon.
Life Cycle and Habits
Both male and female carpenter bees overwinter as adults within their
old nest tunnels. Adults emerge in the spring (April and early May)
and mate. Females provision the tunnels or galleries with bee bread
(mixture of pollen and regurgitated nectar), lay an egg on top of the
mass and close the cell with chewed wood pulp. She excavates the
gallery with her mandibles (mouthparts) at the rate of one inch in six
days. The gallery has a clean-cut round entrance hole with sharp edges
3/8 to 1/2 inch wide (dime-sized) on the lateral wood surface. The
gallery continues inward for one to two inches, then turns sharply at
a 90 degree right angle running in the same direction as the wood
grain for four to six inches or up to 10 feet long, if used by many
bees. Damage from a pair of bees is slight, but if used by many bees
over several years, damage can be extensive.
Each female may have six to eight sealed brood cells in a linear row
in one gallery as she backs outward. Larvae develop on the
pollen/nectar food mass provided, with the life cycle completed in 30
to 40 days. New adults chew through the cell partitions and emerge in
late August. They collect and store pollen in the existing galleries,
return to the tunnels to hibernate and mate the following spring. The
previous year's adults die. They are not social insects and there is
one generation per year.
Control Measures
Infestations are usually first detected by finding large amounts of
sawdust droppings on the ground below the area being drilled or by
observing bees going in and out of the round, circular holes in the
wood affected. These bees attack all species of dried, seasoned wood,
preferring softwoods such as cedar, redwood, cypress, pine and fir.
Nail holes, exposed saw cuts and unpainted wood are attractive nesting
sites. They may refurbish an existing tunnel instead of boring a new
one or new tunnels may be constructed near old ones with infestations
persisting for several years.
- Prevention - Keep all exposed wood surfaces well painted
(oil base or polyurethane) to reduce attack. Wood stains will not
prevent damage. Aluminum, asbestos, asphalt, vinyl siding and
similar non-wood materials will not be damaged. If practical, remove
and replace damaged wood with chemical pressure-treated wood to
discourage nest construction.
- Insecticides - During the daytime, locate tunnel
entrances and after dark, on a cool evening when carpenter bees are
less active, treat directly into the nest entrance and on a wide
area of adjacent wood surface. Do not plug the entrance since bees
should be allowed to pass freely to distribute the insecticide
within the holes. If tunnels are plugged before bees are killed,
they may chew new openings elsewhere. Dust applications are usually
more residual and effective than sprays due to the nature of the
gallery construction. Even newly emerged bees will contact the dust
when leaving the opening. After treatment, some wait until adult
activity ceases or until autumn before sealing the hole with
caulking compound or wood putty. This procedure reduces wood
deterioration and possible future infestation. Be sure to wear
protective clothing to avoid any stings during treatment.
Dusts include bendiocarb (Ficam), boric acid (Perma-Dust), carbaryl
(Sevin) or pyrethrins (Microcare). Other pesticides, either with
some formulations restricted or restricted to be applied only by a
licensed pesticide operator or applicator, include bendiocarb +
pyrethrins (Ficam Plus), bifenthrin (Biflex), chlorpyrifos
(Duration, Dursban, Empire, Engage, Tenure), cyfluthrin (Optem,
Tempo), cypermethrin (Cynoff, Cyper-Active, Demon), deltamethrin
(Suspend), fenvalerate (Tribute), permethrin (Astro, Dragnet, Flee,
Prelude, Torpedo) and tralomethrin (Saga). Homeowners can use liquid
sprays of carbaryl, diazinon, propoxur (Baygon), pyrethrins and
resmethrin. Always read the label and follow directions and safety
precautions.
| This publication contains pesticide recommendations that are
subject to change at any time. These recommendations are provided
only as a guide. It is always the pesticide applicator's
responsibility, by law, to read and follow all current label
directions for the specific pesticide being used. Due to constantly
changing labels and product registration, some of the
recommendations given in this writing may no longer be legal by the
time you read them. If any information in these recommendations
disagrees with the label, the recommendation must be disregarded. No
endorsement is intended for products mentioned, nor is criticism
meant for products not mentioned. |
Source: Ohio State University Extension Fact Sheet HYG2074-94,
William F. Lyon
For additional photos of Carpenter Bees and
the damage they can do  |
