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Powder Post Beetles

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Powder Post Beetles

Powderpost beetle-damaged wood is common in Victoria.

Wood damaged by powderpost beetles has small, round holes 1/6" to 1/8" in diameter. These are the exit holes of the adult beetles. Inside the wood are tunnels filled with fine sawdust and the excrement of immature beetles.
Fine Powder Called Frass Comes Out of Holes and is Noticeable When Wood is Opened.

Fine powder may be observed coming out of the holes or in piles under the holes. The adult beetles are seldom seen.

Adult beetles emerge from the wood from April to July. Eggs are laid in midsummer in cracks and holes in exposed wood. Grubs hatch from the eggs and tunnel into the wood. The grubs feed inside the wood for about one year until they mature

Powderpost beetles will attack the wood structure under buildings, especially if there is a soil floor and poor ventilation. Sapwood with a high moisture content in shaded areas is also attacked. Structural damage to wood is caused by continual reinfestation of the wood. Wood can be seriously damaged even though it looks normal except for the exit holes.


If you are not sure if the holes you see indicate an active infestation, contact us and we can use a specialized moisture meter to determine if the amount of moisture in the wood favours an infestation. Or, you can paint a portion of wood before April, and check it after July to see if fresh emergent holes have appeared.

Powderpost beetles do not survive well under dry conditions. Keep all the wood in your home dry by doing the following:

  • cover soil under the house with a vapour barrier
  • ventilate crawl spaces
  • keep drains working properly
  • do not allow soil to touch wood
  • fix all water leaks

The Building Code provides more details on keeping structures dry.


Professional application of sodium borate to infested wood is very effective. Sodium borate penetrates into the wood and provides long-term protection. The product is only available to licensed professional pest managers.

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