Question

I’d like to build a small log cabin that will be used mostly as a weekend retreat and hunting cabin. In my research, I keep reading horror stories about log cabins infested with wood borers. Is that really a concern? Should I treat the wood with something first?

Answer

Most log home pests infest the wood before construction, shortly after the logs are felled. These wood-boring beetles deposit eggs in the bark shortly after the tree is cut. Unless the logs are debarked within a few weeks of cutting, the larvae hatch and quickly bore into the wood. Inspect logs for infestation before use. This is particularly important if you use fallen or standing dead trees for your logs.

Unfortunately, treating or seasoning the wood won’t completely solve the problem. Debarking and seasoning the wood offers some protection against certain borers. But others, like old house borers and anobiid powderpost beetles prefer seasoned wood. Logs that have been treated with wood preservatives are not fully protected either because natural cracking and splitting of drying logs exposes new, untreated wood for attack.

Many of the same beetles and borers that attack log homes can also be found in conventional frame homes, but they have a hard time surviving the milling process when logs are sawed for stick home construction. Those borers that do survive are not as obvious to the homeowner as borers in the exposed wood of a log home.

How concerned should you be if your log home has wood borers?

The larvae feeding in the wood develop slowly; most of them will emerge as adult beetles within the first couple of years after construction. In general, those borers that attack trees while still standing or immediately after the logs are cut, will not reinfest the wood in a home once they have emerged. They require a high wood moisture content and once the wood dries they are not able to complete development. Any damage that they do to the wood is usually minimal.

Those beetles that attack seasoned wood (old house borer, anobiid powderpost beetle) are capable of reinfesting. And, in fact, your cabin may be more susceptible to reinfestation by these beetles if it is closed up and not heated for long periods. These beetles prefer the higher moisture level found in unoccupied homes. Applying a polyurethane coating or other finish to the surface of the logs will help prevent reinfestation by those beetles that attack seasoned wood.

Unless your cabin is infested with beetles that can reinfest, control of other borers is probably not necessary. In most cases, reinfesting wood borers in log homes are treated by surface application of a penetrating borate product or by pressure injection of various insecticides, including borates. In some cases, seriously infested log homes are fumigated. Infestations are often localized and you may be able to remove and replace infested logs.

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