Powderpost Beetles in Furniture

Other Versions
Spanish Pinholes and powder are a dead giveaway of a beetle infestation. Here are some facts about the bugs and how to handle them. February 19, 2006

Question
A customer has found a few pin holes in a piece of red oak in one of my chairs. She claims they have always been there, but she has just noticed they seem to be generating some fine saw dust. They apparently are mainly in the early growth rings but I am waiting for her to ship the piece (a bench via UPS) back to me.

I have not had any problems with red oak or any other wood in my shop or any other customer having problems. What are they? What treatment can I use? The finish is Watco Danish Natural Oil and paste wax. The piece only has the critters in stretchers from the same dowel and there is nothing in the legs or the other two stretchers.

Forum Responses
(Furniture Making Forum)
From contributor H:
Most likely the wood was only air dried. Those critters can lay dormant for years. Getting rid of them is easy. Get rid of the piece they’re in before they spread.

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From contributor S:
These beetles are usually found in green wood and die when the material is kiln dried. If the material has the beetles in it already they can spread rather quickly to the rest of the piece. I do not know of any way to get rid of them once a piece is built.

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From Gene Wengert, forum technical advisor:
Let me correct some of the information provided: There are different types of powder post beetles. You are dealing with lyctid PPB. This insect prefers drier wood, down to 8% MC. Other PPBs like wetter wood. It is typical to get this beetle after kiln drying, not in green wood or in air dried wood.

The PPB in furniture cannot be controlled with chemicals, as the insect is deep within the wood and any chemicals stay at or near the surface.

It is difficult in a piece of furniture for them to leave the wood and for "Ma and Pa" to find each other, breed, find a grainy wood to lay eggs, etc. So, you do not have to worry much about spreading, but the home-owner may not accept this. Of more concern is the damage (strength loss) done to the wood.

All wood that is kiln dried above 130 F is free of PPB and their eggs. So, it is likely that the infection developed when your wood was exposed to other infected lumber after kiln drying. In fact, you do have a risk that it will show up elsewhere in the next year. Springtime is the most common time. Your lumber supplier is probably the source and you may wish to consider changing suppliers. If they have the infection, it will likely continue to show up in the future.

They will remain active for several years. They will not re-infect wood with a smooth finish (varnish, etc.) but can do a lot of damage in the pieces where they are present. It should be removed from the house as soon as possible. It needs to be replaced. Keep the infected pieces and furniture away from all other wood, especially unfinished wood or lumber. Heating the piece (or lumber) to 130 F for a day will kiln the insects and their eggs. It is not uncommon for insects to show up a year after infection.

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From the original questioner:
Thank you Gene. It is interesting that the bugs are only in the one dowel that was used to make the two main (longest ones) stretchers and not the side stretchers that were another dowel. The legs were from different stock from another supplier. I have checked the other oak dowels from my stash and nothing is showing up. Is red oak more likely to get the infestation versus maple, walnut, cherry and white oak? I have seen the results of little critters in cherry where they burrow.

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From Gene Wengert, forum technical advisor:
They strongly prefer a grainy wood with nooks and crannies and not a smooth wood.