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University
of Rhode Island GreenShare Factsheets
Powder
Post Beetles
Families Lyctidae, Anobiidae &
Bostrichidae
There are number of insect species
belonging to three separate families which all share the
common name "powder post
beetles." Adults of these families lay eggs in or on seasoned
wood, including untreated wood surfaces in the home (furniture,
wood floors and structural timbers), firewood and lumber stock
piles. The larvae tunnel through and feed on the wood, converting
it to a fine powder. When mature, the adults emerge to mate,
leaving the wood surface perforated with small, round "shotholes." Powder
post beetles may degrade the quality of lumber, destroy furniture
and wooden tools and, in rare cases, they may completely destroy
the structural integrity of buildings.
Lyctus beetle adults are 3-5 mm (1/8-1/5 inch) long, reddish-brown
to black, and somewhat flattened, with the head distinctly
visible from above.
Anobiid beetle (furniture beetle
and death-watch beetle) adults are 2-5 mm (1/10-1/5 inch)
long, reddish-brown to dark
brown and covered with fine yellow hairs. Anobiids
are cylindrically-shaped--the head is hidden by the thorax
when viewed from above.
Bostrichid beetle adults are 3-6 mm (1/8-1/4 inch) long,
dark brown to black, cylindrical in shape, and have an enlarged
thorax which gives the beetle a humpbacked appearance. The larvae of these beetles are seldom seen because they
live entirely inside wood. Mature larvae are 5 mm (3/16 inch)
long and are white with brownish heads and dark mandibles when
mature.
Lyctus beetles commonly produce one generation per year.
Females lay their eggs in the natural pores of timber, infesting
only the sapwood of seasoned hardwoods. Eggs hatch in several
days and the larvae tunnel into the wood. After pupation, the
adults emerge (usually in June), leaving round shotholes on
the wood surface. After mating, females will often reinfest
the same timber.
Anobiid females lay their eggs on the surface cracks and
crevices of wood or in the mouth of old exit holes. Anobiids
usually attack the sapwood of seasoned softwoods. Eggs hatch
in about a week and the larvae tunnel into the wood. Larvae
may live for one to four years. After pupation, the adults
emerge, mate and usually reinfest the same timber.
Bostrichid females bore tunnels into
the wood to lay their eggs. Eggs hatch in approximately 21
days and the larvae mine
the wood for nine months. In another 30 days the mature beetles
emerge, mate and usually reinfest the same wood. Bostrichids
prefer the sapwood of seasoned hardwoods, though they do attack
softwoods.
• Powder post beetle infestations
are most often initiated by introducing infested material
into the home. Avoid
storing firewood in the home for more than two to three days
prior to its use.
• Any building materials
introduced into the home should be checked for signs of beetles,
damage or larvae.
• A coating of shellac, varnish,
wax or paint may prevent an infestation, as Lyctus beetles
and Anobiids are
unable to oviposit if the pores in the wood are filled. Filling
in already existing shotholes can help prevent a reinfestation,
if holes are continually filled as new adults emerge.
• Powder post beetles cannot
survive in dry wood. Often the long-term solution to a powder
post beetle problem
is to reduce the moisture level of the wood by reducing humidity.
This may involve installing a concrete floor in an old basement
and/or installing a dehumidifier.
• Insecticides may be necessary
for all but very light infestations in structural timbers.
Insecticide solutions
are generally painted on the wood surfaces. Professional extermination
is often necessary. Boric acid treatments have been shown to
be effective in control of powder post beetles.
By Eleanor Groden, David
B. Wallace, and Richard A. Casagrande. Revised 1999.
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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