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Powderpost Beetle Infestations

- Typical infestations of wood boring beetles -

Summary: Wood boring powderpost beetle infestations occur in both softwoods and hardwoods. Softwood infestations typically occur in structural wood like beams and joists while hardwood infestations occur in flooring, furniture and cabinets.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Beetle infestations in softwood and hardwood

Powderpost beetles,sometimes called woodworms, are wood boring beetles that infest both softwoods like pine, fir, spruce and hardwoods like oak, maple, and ash. Unlike most other insects that damage wood (see Wood Destroying Insects), powderpost beetles have the potential to start a cycle of infestation that may last many years and do significant damage to the wood they infest.

Infestations of these beetles can have serious economic impact. Significant damage to hardwood flooring and cabinets can occur as well as weakening of structural timbers like posts, floor joists, subfloors, and other framing materials. Suspect infestations can also interfere with real estate transactions even if the beetles are no longer active.

kitchen cabinet with powderpost beetle holes

Lyctid powderpost beetle emergence holes in the face frame of a kitchen cabinet (look carefully below the shadow).


Some examples of powderpost beetle infestations

Infestations usually come in one of two varieties: infestations in softwood structural timbers like floor joists, posts, beams, or, infestations of hardwoods such as flooring, furniture or cabinets. The following examples illustrate some fairly typical situations.

  • Scenario 1: Beetle infestations in structural wood affecting sale of home

  • During a pest and dry-rot inspection of a newly renovated house powderpost beetle emergence holes and fresh boring dust are found in some structural timbers in the crawl space under the house. The home inspector reports this to the potential buyers who promptly pull out of the transaction because they are afraid of the beetle infestation. The homeowners want to know if the infestation is active and how to treat it so they can get the house back on the market.

  • Options: Structural wood like softwood beams and posts can be treated with a borate-based wood preservative such as Bora-Care that will prevent re-infestation. Larvae that are still developing inside the wood are difficult or even impossible to treat but the borate treatment will disrupt the infestation when these larvae emerge as adults.

Insecticides to treat powderpost beetle infestations

  • Scenario 2: Beetle infestation found in hardwood cabinets, owner threatens to sue cabinet maker

  • A cabinet maker is faced with replacing the kitchen cabinets in 40 apartments because the wood frames made of the hardwood poplar show the characteristic signs of a powderpost beetle infestation (emergence holes and powder or boring dust, see image above). The primary concern is "will emerging beetles be a threat to other wood in the apartments?"
  • Options: Other nearby hardwoods will not be attractive to emerging beetles if they are varnished or painted. However, new, unfinished wood can become infested so it should be treated with a borate-based insecticide such as Bora-Care or Timbor. Both materials are water-based and can be simply "painted" on these surfaces where the borate is absorbed into the wood.

  • Scenario 3: Beetle infestation found in hardwood flooring. Where did it come from, when did it start?

  • Hardwood flooring is sometimes infested with lyctid powderpost beetles that begin to emerge a few years after the flooring is installed. Emerging beetles leave behind holes and "frass" or small piles of boring dust made of fine wood fragments. Concerns range from "do the beetles pose a threat to other wood in the home?" (see scenario 2 above) to "when did the wood become infested and therefore who is legally responsible?" and, "how much damage will eventually occur?".
  • Options: This situation is the most complex of the three scenarios. The question "when/where did it start" largely depends on when the floor was installed and the rate of beetle emergence. Infestations typically begin at the manufacturing plant even if the stock wood was kiln-dried. Stock that is not stored properly can become infested if exposed to a nearby active infestation. Emergence of the subsequent infestation can occur over several years following installation. See Related Articles below for various control options. Contact me if you need assistance evaluating a particular situation.

Related Articles

What are Powderpost Beetles?

Powderpost Beetle Control & Prevention

Powderpost Beetle Damage in Hardwood Flooring & Furniture

Using Bora-Care & Shell-Guard Wood Preservatives

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