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Holes and Sawdust in Hardwood Stairs

By Chris Williams on December 9, 2013.
hardwood stairways

Question

My mother just moved into a new townhouse about 14 months ago. In the last two weeks, she has been finding tiny holes in a couple of her hardwood stairs. In some cases, there are little piles of sawdust underneath the holes. We haven’t seen any termites. What else could be tunneling in the wood? I don’t want to break the stairs open if I don’t have to.

Answer

Yes, we can rule out termites. They don’t make little holes and they don’t leave piles of sawdust. It sounds like you’re dealing with some type of wood-boring beetle, most likely the lyctid powderpost beetle. But before any action is taken, you should have an inspection to determine the extent of the infestation and to verify identification of the pest.

How Did the Infestation Start?

Powderpost beetles typically infest hardwoods during drying time or in storage, and lyctids are generally brought into buildings in wood that contains their eggs or larvae. The beetle problem is literally built into the house, and the wood is often finished or sealed after construction.

The larvae feed in the wood, tunneling along the grain. The “sawdust” that you see is actually beetle feces, tiny pellets of digested wood. Depending on the type of powderpost beetle, the sawdust may be packed tightly in the larval tunnels, or it may be loose. After the larvae pupate and turn into adult beetles, the adults bore tiny, round exit holes in the wood. As they leave the infested wood, they push the sawdust out.

Inhomes, lyctid powderpost beetle infestations are typically discovered between one to two years after construction. In this case, we know that this is a current, active infestation. No doubt your mother is sweeping up the sawdust and then finding more the next day. If you look closely, you might find the tiny, dark adult beetles around windows or lights. Save them for identification.

Will They Reinfest Other Wood?

If these are lyctid powderpost beetles, you should expect them to emerge from any infested wood during the next few months and that should be the end of the infestation. I assume the new stairs have polyurethane or some other finish. Although powderpost beetles can emerge from sealed wood, they will not lay eggs in wood that has been finished so there is no concern about emerging beetles reinfesting the stairs or any other finished (painted, lacquered, varnished) hardwoods in the townhouse. That’s some comfort.In rare cases, they could infest unfinished hardwoods in the home, or could lay eggs in the unfinished back side of the stairs.

Your immediate concern though is to limit the damage to the stairs by emerging beetles. There are a number of control options in this case that range from simply replacing the infested boards (if there are only a few), to treating the wood with a borate product, to injecting the wood with a special insecticide.

One of your first steps should be to contact your builder. He may even arrange for the pest control inspection. The townhouse is probably under some kind of warranty that would cover either replacement of the stairs or appropriate treatment.

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