Powderpost beetles – The other, other wood destroying insects
Editor’s note: This article is from the archives of the MSU Crop Advisory Team
Alerts. Check the label of any pesticide referenced to ensure your use is
included.
I routinely get calls requesting information on powderpost beetles.
These calls are usually from people interested in preserving old barns,
people with Michigan basements or people who discover piles of powder
under a recently purchased piece of furniture or artwork. Unlike
termites, which leave very little external evidence of their activity,
powderpost beetles provide tell-tale signs of theirs. As their common
name suggests, powderpost beetles often leave a pile of very fine powder
under the wood in which they are feeding. The powder sifts out of the
wood through the emergence holes chewed by new adult beetles exiting the
wood to find mates and lay a new generation of eggs. These small, (less
than 1/8 of an inch) round holes are another sign of a powderpost
beetle infestation.
The term powderpost beetle can refer to several species of
wood-destroying beetles that belong to three (now two) different
families of beetles: Lyctidae (formerly), Bostrichidae and Anobiidae).
Only lyctid powderpost beetles produce the fine white powder that gives
this group of beetles their common name. Anobiids or deathwatch beetles
do not produce piles of powdery frass. They pack their frass in their
feeding galleries.
Powderpost beetles are second only to termites in their ability to
destroy wood in structures and furniture. They are capable of
re-infesting dry, seasoned wood year after year. The interior of the
wood that is repeatedly attacked is completely riddled with holes and
galleries packed with the powdery frass. Powderpost beetles can infest
any untreated or non-sealed wood article. Some species only attack
hardwoods, while others feed only on softwoods, and some species will
feed on both. Under normal conditions, powderpost beetles require about a
year to complete their development. However, if the wood has a high
moisture and starch content, development may be completed in six months.
The moisture content of the wood is a very important factor in managing
powderpost beetles. Wood should be maintained below 20 percent moisture
content to reduce its suitability to powderpost beetles. Some experts
believe if the wood is kept dry enough, then no insecticide application
is necessary, but I’m not sure that I agree with this.
Powderpost beetles can also be controlled by sealing the surface of the
wood with shellac, paint or varnish which discourages female powderpost
beetles from laying eggs on these surfaces. Chemical control of
powderpost beetles includes three options. Fumigation with a penetrating
gas (like methyl bromide) is the most effective means of chemical
control, but it is also the most expensive, and in most cases,
prohibitively so. Fumigants are the most dangerous type of insecticide
and can only be applied by a professional applicator with special
certification.
Insecticide sprays applied to wood surfaces are also effective in
controlling powderpost beetles. Tempo (cyfluthrin) and two borate
products called Bora-Care and Tim-Bor are the only registered
insecticide sprays that can be used in occupied structures. Borates can
be applied at anytime, but two applications are required to provide
effective control. Borates must penetrate the wood to be effective,
therefore, it should not be used when the wood to be treated has been
painted or sealed with polyurethane. Bora-Care can be purchased from an
outfit in Maryland called PRG (short for Preservation Resource Group) at
(301) 309-2222. If you interested in Bora-Care, call these folks and
they will send you a brochure about their product line or see them on
the web at http://www.prginc.com.
Tempo (cyfluthrin) is also available under the brand name Bayer Advanced
Garden Insect Control or Bayer Advanced Home Insect Control. It must be
applied just before the adult beetles emerge in late spring to be
effective. Tempo should be applied in mid-May and again around the first
of August. Eye goggles are a must when treating for powderpost beetles
when you will be spraying areas above your eyes. Provide good
ventilation when applying any insecticide indoors. Be sure to read and
follow all the instructions and safety precautions found on the
pesticide label before using any pesticide.