What are Powderpost Beetles?

Stephanie L. Richards, PhD, Medical Entomologist

Powderpost beetles are wood-boring beetles (Family Bostrichidae, subfamily Lyctidae) that primarily impact unfinished, unpainted and/or unsealed wood that has low moisture content. When it comes to causing structural damage, they are second to termites that also inflict damage to wood products.

Powderpost beetles are known to inflict damage to products, such as:

  • Wooden beams (barns, cabins, homes)
  • Hardwood floors
  • Cabinets
  • Musical instruments
  • Furniture

Some species of powderpost beetles have been inadvertently distributed worldwide due to the timber industry. Some powderpost beetle species feed on a wide variety of different types of wood, while others may be more specialized to feed on a particular type of wood/plant (e.g., bamboo powderpost beetle Dinoderus minutus).

What are the signs of a powderpost beetle infestation?

Mated females of some species of powderpost beetles bore into wood and lay their eggs either on the surface of untreated wood or in tunnels just below the surface, while other species lay their eggs in cracks within the wood. Infestations develop relatively slowly and beetle larvae generally spend years chewing through wood materials (primarily ingesting starch, sugar and protein), expelling wood waste that has a powdery consistency (hence the name, powderpost beetle). Powderpost beetle larvae cannot digest cellulose or lignin components of the wood. These wood-boring beetles make tunnels through the interior of the wood, hence weakening its core.

Since larvae may be boring deep into the wood, infestations can be difficult to detect until damage has already occurred. When mature larvae are ready to pupate, they travel to an area near the wood surface to build a pupal chamber. This inactive pupal stage can last up to a month. Evidence of a powderpost beetle infestation includes wood powder on the ground and tiny holes where adult beetles have emerged from the wood. Depending on location, adult beetles emerge from wood during spring/summer months. In most (but not all) cases, infested wood contains eggs/larvae when it is first installed in a home and this may be due to improper drying or storage of the wood. If beetles are observed on finished wood, they were likely present before the wood was sealed.

What should I do if I suspect a powderpost beetle infestation?

Pest management professionals may be consulted to assist in surveillance, assessment and potential treatment of an infestation. If fresh, powdery (sawdust-like) piles are observed near exit holes in wood, this may indicate an active infestation. In infestations that are no longer active, exit holes may not exhibit a “freshly drilled” appearance but would have a more weathered look. Cleaning up powder and then revisiting the area to check for new piles of powder is one way to help evaluate a potential infestation. Infestations may vary seasonally, with most occurring in spring/summer periods, depending on geographic location.

If powderpost beetles are suspected to be infesting wood in crawl spaces, a moisture barrier may be considered as an option to reduce beetle abundance since some species require moisture for survival. If only a few boards seem to be affected, replacement of the boards can be considered after pest management professionals have managed the infestation (if needed).