Wood-boring Beetles in Log Homes
By Chris Williams on February 26, 2013.
We have a vacation cabin near Wachusett Mountain that we visit a few times a year. The cabin was built just five years ago. Last week when we were there, I noticed piles of sawdust on the floor in one corner of the main room and a couple of holes in the logs directly above the sawdust. Do we have termites? How are they treated in a log home?
Not termites; subterranean termites don’t leave either piles of sawdust or holes in wood. Carpenter ants can leave piles of “sawdust,” but no actual emergence holes. My guess is that you have some type of wood-boring beetle emerging from your logs. The beetle larvae tunnel and feed inside the logs, sometimes for years, and the resulting adult beetles tunnel out, leaving exit holes and piles of sawdust.
There are two types of wood-boring beetles: those that infest only live trees or recently felled trees, and those that infest dry, seasoned wood. It is usually not necessary to treat beetles in the first category because the beetles will not reinfest the seasoned logs in your home. Beetles in the second category are the problem.
You don’t say how big the holes are. Exit holes in wood vary in size, depending on the size of the adult beetle emerging. Very small circular holes belong to powderpost beetles which infest seasoned softwoods and hardwoods. They usually begin to emerge from the logs during the first year or two after construction. These little beetles can reinfest the logs that they emerged from but they usually cause minimal damage overall.
Of more concern is the old house borer. This is a much larger beetle that leaves a larger, oval exit hole. Its larger larvae can do significant damage to wood if enough larvae are present. The name “old house borer” is an unfortunate misnomer because this beetle is mainly a pest of new homes, those less than 10 years old. The female beetle lays her eggs in felled logs or wood stored in a lumberyard, and the beetles are actually then built into your log home. Old house borers usually emerge within 2-3 years of log home construction, but could be expected to take longer in a cabin that is unheated part of the year. These borers can continue to reinfest log homes and usually require control.
Your Control Options
There are a range of control options and you should consult with us or another pest control company to find the best solution for your specific situation. Wood borers can be treated by a surface application of a penetrating borate product or by pressure injection of various insecticides. Some insecticides can be injected directly into the larval galleries in the logs or into drilled injection holes. In some limited infestations, the infested or damaged logs can simply be replaced. Infested log homes can also be fumigated. Contact your log home builder to see if you have a warranty that covers post-construction damage from wood-boring pests.