Powder Post Beetle Infestation

Don't put those timbers in your house. January 29, 2009

We have cants that are going to be used in a post and beam structure. They are red oak and are stickered waiting to be used. They have powder post beetles in them as evident from the small pin holes and small mounds of saw dust. These will not be kiln dried. We have oiled a few of the cants and the beetles remain. Should we be concerned? We they eventually go away? This will be an addition to the hose and will be enclosed and heated when it is done.

Forum Responses
(Sawing and Drying Forum)
From contributor S:
Yeah, they'll go away after they've eaten their fill and then they'll move on to the rest of the structure. I wouldn't use them in my house. You could try to fumigate them but heating the cants would work better.

From Gene Wengert, forum technical advisor:
I agree with contributor S. The strength loss over time will be serious. Heat the wood over 130 F (through and through) and that will eliminate the critters at that moment. However, if the insects are in the dust or in other pieces of wood nearby, when you take the oak pieces out of the heat treater then these oak pieces can be re-infected. Heating or fumigation only provides insect free wood at one point in time and not in the future. Also, the insect (lyctid powderpost beetle) can spread to other hardwoods. I hope you appreciate the seriousness of this infection.

From contributor D:
Thanks for the advice. These are cants that are mostly 8x10. The pin holes are so small you can hardly see them (literally smaller then a pin hole). The amount of sawdust that is pushed out of the hole amounts to a couple of grains of sand. In a 15' length, there are about 30 or so. Will this compromise the strength of the cant? Can I locally treat each small hole? After the cant is worked it is placed in another building away from the pile. Can I force a chemical into each hole and kill the beetle? Not every cant has them - maybe 10%.

From Gene Wengert, forum technical advisor:
PPB makes holes smaller than 1/16". (So does the ambrosia beetle, but the ambrosia beetle likes wetter wood.) The holes are actually exit holes when the insect leaves. Pieces without holes may develop them in the next year or two as insects presently inside the wood leave.

The damage on the inside can be small or large. If the insects breed and lay more eggs and a new crop bores inside the wood, the strength will deteriorate even more. This cycle can continue in use as PPB likes drier wood.

There is no way that anyone can tell how much strength is gone now. Incidentally, if you bought the beams, return them for a full credit. Then fumigate or heat treat all the future beams and avoid having any PPB wood brought into the home.