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Powder Post Beetles and
other wood destroying beetles

Overview

The powder post beetles term usually refers to three groups of insects. The Lyctid/true powder post beetles, Anobiid powder post beetles and false powder post beetles. This name is basically derived from the larvae capability of these insects to reduce dead or dried wood resources to a mass of powdery materials. The true powder post beetles belong to the subfamily Lyctinae from the family Bostrichidae, which includes beetles commonly breed in and feed on dead and dried hardwoods throughout the world. However, about 11 species of them are known in the US.

Besides Lyctid powder post beetles, Anobiid powder post beetles are also considered among the most frequently encountered powder post beetles infesting seasoned wood and timber structures. This group of beetles belongs to the Anobiidae family and is worldwide-distributed insects as well with about 310 species occurring in the US. Anobiid powder post beetles are sometimes called “furniture beetles” as they are commonly found infesting both hardwood and softwood furniture, such as tables, chairs, TV stands, cabinets, benches, as well as bed headboards and footboards.

Some Anobiid powder post species, such as Xestobium rufovillosum are called “deathwatch” beetles. Mutually, males and females of these species produce a tapping sound, as a mating call, by striking the frons of the head (the upper anterior portion of the head of an insect) just above mouthparts on the wood surface of their tunnel. Males usually initiate a sequence of taps, to which females reply. Incidentally, the tapping sound of these beetles was once believed to be that death was near, especially when people were sitting up with an ill person in a quiet night, and hence the name “deathwatch” beetles.

Another wood-destroying beetles from the family Bostrichidae are known as false powder post beetles. These beetles infest floors, furniture, hardwood paneling, and other wood materials. Although they prefer hardwood, false powder post beetles also will attack softwood.

Another example of wood destroying beetles is the old house borer. This species belongs to the beetle family Cerambycidae, a group of insects known as the "longhorned” beetles. Despite of their name, old house borers actually infest wood less than 10 years of age and can cause serious cosmetic, as well as structural, damage.

As you may have heard about termite problems, especially in the southern sates, and how they can cause hundreds of millions of dollars of damage to the US homes each year. As well, the true powder post beetles are considered the second in importance to termites as wood destroying insects. Although these beetles attack only bare wood materials still, finished wood products can also be infested as the infestation may occur before applying finish materials or even before the wood is seasoned. However, a typical damage of powder post beetles can vary from unpleasant holes in a wood surface to significant wood destructions. Similar to termites, severe infestations of powder post beetles can cause the homeowners to spend thousands of dollars in repair costs. But unfortunately, their damage is not usually detected until people start to see fine sawdust particles and small exit holes where adult beetles have emerged.

In this article, we will focus on the powder post beetles as well as the old house borer. For simplicity’s sake, other wood destroying beetles, including, but are not limited to, flat-headed borers, round-headed borers, bark beetles, ambrosia beetles, cedar tree borers, etc will not be covered in this work.

Facts

• Adult powder post beetles fly and are attracted to light.
• The actual food of the larvae of true powder post beetles is the starch present in the cells of the sapwood they infest. This explains why these beetles breed only on certain kinds of timber and then only the sapwood.
• The deathwatch beetles (Xestobium rufovillosum) generate mating calls by striking the frons/front of the head on the substrate 4–11 times, at a frequency of about 11 Hz. Females responded more readily to male beetle taps containing high strike numbers.
• The old house borer essentially attacks new houses just four to seven years after construction. This pest is native to North Africa and is believed to have arrived in North America around 1875.

Identification

Biology

• Adults of powder post beetles usually emerge in the spring.
• After mating, females of lyctid and anobiid beetles locate unfinished wood materials and then lay their eggs in holes, cracks, crevices, or old adult’s exit holes. Differently, the females of false powder post beetles bore into the wood in order to lay eggs, leaving a hole larger that 1/8 inch.
• Newly hatched larvae bore into and feed on the wood causing the damage. As the larvae feed, they create tunnels (galleries) that become filled with powdery frass (insect debris). The shape, size and the appearance of the frass in tunnels are used to determine the pest species causing the damage.
• Larvae development and feeding occur entirely below the wood surface, and can last three months and up to 15 years depending on a variety of factors including, but are not limited to, the insect species, temperature, and the starch, sugar, protein and moisture contents of the infested wood. Usually, larval development last:
  • Three months to 12 years for Lyctids
  • One to two years for Anobiids
  • One to five years for Bostrichids
  • 3-15 years for Cerambycidae

• At favorite conditions, fully-grown larvae tunnel towards the wood surface to pupate.
• Adults finally emerge in one to four weeks depending on the species leaving noticeable frass under or around the edges of the exit holes.
• Adults emerge shortly, mate and repeat the life cycle.

Habits

Larvae live and feed inside the wood. Newly emerged adults chew their way out of the wood, and are attracted to light. They tend to gather around windows and lighted areas.

Management /Prevention

• In your constructions, don’t use infested wood materials, but instead use treated wood with long lasting insecticides or wood preservatives.
• To prevent adults from laying eggs, sand and seal cracks, crevices and holes in the wood surfaces and then brush on a wood preservative (paint, water repellent stains, varnish and wax).
• Use building with good ventilation, drainage and clearance between wood and soil.
• Use proper furnace, air-dried wood, central heating and cooling systems to accelerate the wood drying process and reduce moisture content to below 8%.
• Install a moisture barrier or increase ventilation especially in the crawl space of infested buildings.

Heat Treatment

• Heat treatment at 120-140°F (49-60°C) for 6 hours kills all life stages of powder post beetles. While, 190°F (88°C) kills old house borer larvae.
• Freezing at 0°F (-18°C) for 72 hours may kill powder post beetles. However, if the wood is thicker than 2 inches, a longer treatment time is required.

Pesticide Treatment

• In order to effectively manage powder post beetles and other wood destroying beetles, pesticides with high penetration capability and extended residual longevity such as Bora-Care® and Tim-bor® (a slow acting stomach poison) need to be used. Even so, Bora-Care® or other liquid pesticides do not penetrate wood has polyurethane finish, paint, varnish or a water-repellent stain. They need to be applied only to bare wood, plywood, particleboard, and other cellulosic surfaces. Therefore, infested finished wood must be stripped before treatment and re-coated afterward.
• If the finishes cannot be removed, deep penetration is still needed to manage the developing larvae inside the wood. In this situation, the wood surface can be drilled and the Bora-Care® or Jecta Gel® (a concentrated form of Bora-Care® in a gel base that is delivered by a plastic syringe) is applied inside the holes. These holes need to be sealed after treatment or the gel will leak out. In case of severe, extended, and rapid elimination of powder post beetles is desired, especially when other methods have failed, a fumigation is another option to be considered for managing these insects; however, fumigation does not prevent from re-infestation of the wood, thus, treat with Bora-Care® to prevent future infestation. Note that fumigation requires special preparations and precaution measures before treatment. For thin pieces (baskets and wreathes), adult exit holes can be treated individually with a crack and crevice aerosol (e.g., Invader). It is also recommended to treat with Bora-Care® later to ensure longer residual effects. However, homeowners, building managers or their agents, need to know that the treatment with Bora-Care® will stop the development of the chewing larvae quickly and prevent later infestation, but adults may be still seen for a while until all developing pupae have emerged.

FAQ

Q: One of my clients has noticed sawdust wood materials and pinhead size holes on chairs that I sold her a couple of months ago. She claimed that the holes were there before she purchased the chairs. These chairs are made of oak with Comfort Arm Chair Finish on them. I never had problems with oaks before.  I am expecting to receive these chairs back within a week from now. What they are? What shall I do?
A: It is most likely that the chairs are infested with true powder post beetles/lyctid powder post beetles. I am assuming that the chairs were infested before they have the finishes on them. Since true powder post beetles can re-infest seasoned unfinished/ bare hard wood, I recommend fumigating these chairs before bring them in and then treating with Bora-Care®. Another option is to heat infested chairs at 130-140°F for 6 h or a day. The best solution is to get red of them before they spread and infest unfinished furniture.

Q: I have found a small pile of sawdust particles near the baseboard in my bathroom, every time I vacuum it away, a few wood materials starts appearing until it becomes a small pile in three or four days. I cannot see any insect nor can I see where the wood particles are coming from. Do I have to rip up the baseboard and linoleum to check, or do you have any idea what could be causing this? How do I get rid of this problem? Thank you
A: It does not sound like termites. Before ripping up the baseboard, check the texture of the sawdust to know whether the insects are powder post beetles or carpenter ants. Carpenter ants produce coarse sawdust-like material that is pushed out from the nest. The sawdust may include other debris such as dead ants, parts of insects and other food; while, powder post beetles produce fine, powder-like sawdust.