Worm holes
February 13, 2013 | 6:00 pm CST

Q: I just received some kiln-dried hardwood lumber that has worm holes in it. Is there a risk of having this lumber with worm holes perhaps having living bugs in the holes, infecting other dried lumber in my warehouse?

A: The risk of infecting lumber and such an infection causing a problem is very, very small. You will understand this answer better if we review a few facts:

Almost all insects that infect wood prefer wet wood. There are only two common insects (in addition to termites) that infect dry wood -- the lyctid powder-post beetle (grainy hardwoods only) and the old house borer (softwoods, especially pine, only). Even these two insects that like dry wood prefer wood 8 percent MC or wetter. Drier wood is just too hard for them to eat. Most kiln-dried hardwoods are drier than 8 percent MC.

Second, kiln drying (if the temperature went over 130 F, which it does in 99 percent of the kilns) will kill all insects and eggs. So, when the lumber leaves the kiln, it is sterilized.

Third, it takes months to years for newly laid eggs to hatch, burrow into the wood and then burrow out, leaving the visible exit hole. When you see holes in lumber that has been recently kiln-dried, there has not been enough time to have a new infestation of insects make those holes.

Fourth, the powder-post beetle makes holes that are 1/16 to 1/32 inch in diameter. Any larger holes in kiln-dried hardwood lumber would not be a risk factor, as the insects are not "dry wood insects."

Fifth, even if you see small-diameter new holes with a living insect, it still takes "two to tango." The risk of breeding new insects is a rare event if sanitation (no wood debris, no socializing or breeding grounds) is good to excellent.

Sixth, there is an incubation period, once new eggs are laid, of up to two years. Survival of the eggs in a piece of furniture machined or sanded so the surface fibers where the eggs were laid is gone, coated with a finish, heated in finishing ovens, and so on is quite rare.

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About the author
Gene Wengert

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 45 years. He is extension specialist emeritus at the University of Wisconsin-Madison.