Wood-Boring Powderpost Beetles

-- Small beetles that infest wood --

Summary: The term "powderpost" beetle refers to the type of damage done by several different wood-boring beetles. The larvae of powderpost beetles infest both hardwoods, like oak and ash, and softwoods like pine and fir. Larvae develop feeding on starch contained in wood cells. As they tunnel a fine powdery sawdust is left behind. After a long development, that depends on the quality of the wood, larvae become adults that emerge through the wood surface. Emergence holes are usually surrounded by tell-tale piles of the fine powder for which the beetles are named. Larvae are sometimes called "woodworms".

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Jack DeAngelis, ext. entomologist (ret.) revised: 11/2018

Woodworm & powderpost beetle damage potential

Powderpost beetles are potentially the most destructive beetle pests of seasoned wood (termites are more destructive of all wood overall, however). These small, wood-boring insects may damage both hardwoods such as oak, maple, and ash, as well as softwoods like pine, fir, and spruce.

What makes these beetles so potentially damaging is their ability to repeatedly infest relatively dry, seasoned wood over many years and many generations of beetles. There are other wood-boring insects that are less important because they do not infest wood after the first generation which limits their damage potential (see A List of the Wood Damaging Insects for descriptions of these pests).

While larvae (grubs) do all the damage by their tunneling and feeding adult beetles are the ones most often seen. Adults typically are small, elongated brown beetles (see photo below).

lyctid (Lyctus) powderpost beetle

A lyctid (Lyctidae) powderpost beetle, ~ 1/8" long.

Species that infest softwoods tend to be the most damaging because they potentially weaken buildings when they damage structural wood such as beams made from pine or Douglas-fir. Fortunately, softwood-infesting species are somewhat easier to control. The species that infest hardwoods cause mainly cosmetic damage but can also do some structural damage to wood floors, cabinets and furniture and can be more difficult to control (see Damage to Floors, Cabinets and Furniture).

Powderpost Beetle Treatment Options

Infestations can often be managed or prevented with relatively low toxicity wood preservative based on sodium borate, such as Timbor or Bora Care, applied to the wood surfaces. In other situations the best approach may be simply to monitor with "watchful waiting" (see How to Treat Wood Boring Beetles to explore these options).

Development of powderpost beetles/woodworms

Wood-boring powderpost beetles spend most of their lives as larvae ("woodworms") in wood where they tunnel in search of the starch and other nutrients they need. Development time varies depending on temperature, moisture and starch content of the wood but can last months to several years, and even longer for some species.

Once they complete development larvae tunnel back to the wood surface where they pupate to adult beetles. Beetles chew the last few millimeters and emerge through round emergence holes pushing out a fine boring dust ahead of them (see Powderpost Beetles and Hardwood Floors for a picture). Adult beetles live only long enough to mate and lay eggs for the next generation. Eggs are laid on unfinished wood because young larvae cannot bore through varnish or paint.


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