Working the Bugs Out of Firewood

With cold weather approaching, those of us who heat with wood look forward to the cozy warmth that only a wood fire can provide. Especially if it’s a fireplace, or a stove having a window so you can watch the flames, it’s the kind of ambiance perfect for sharing with loved ones on frigid evenings. With the Covid-19 situation, however, visitors may be fewer and far between for a while.

How to deal with uninvited guests can be a quandary. When crawly things start coming out of the woodwork, or more specifically, the fuel wood, there’s nothing we’d like more than some physical distancing. As wood we lug inside thaws out, any critters hiding under the bark feel like winter is over, and gleefully venture out. For different reasons, both insects and homeowners are both disappointed.

The good news is that one can take steps to discourage critters from making your woodpile their condo in the first place. Also, most of these guests are not dangerous, but merely nuisances who just want out. The bad news is, well, they’re a nuisance. The two types of firewood crawlies are shelter seekers and wood borers. Both kinds of stowaways usually head for a window where you can let them out or…something.

Shelter seekers just need a place to crash for the winter, and would be as happy in a brush pile as in a firewood pile. These include crawlies like caterpillars, ladybird beetles, spiders, and centipedes.

Wood borers range in size from less than one-eighth up to three inches long, but most are on the small side. The largest are roundheaded borers, of which the white-spotted (pine) sawyer and its similar, sinister cousin the Asian longhorn beetle are examples. Flatheaded borers include the native bronze birch borer as well as the invasive emerald ash borer. Ambrosia and elm bark beetles are small and they stay just under the bark and don’t enter the wood.

With some notable exceptions, wood borers seek dying or just-killed trees, sometimes arriving to lay eggs hours after a tree is felled. Obviously they don’t need social media to keep up on news. They do need moisture, though, which plays into control options.

If conditions are right, it’s possible for certain insects to cause trouble. Tiny powderpost beetles (one-sixteenth of an inch) can infest bare hardwood in high-moisture environments. In the heating season your living space is too dry for them to survive. But firewood stored in a basement could be an issue if the joists are unpainted hardwood, which is sometimes the case in very old homes. Carpenter ants also need moisture to set up housekeeping. Unlike termites, they can’t eat wood, and can only make nests where moisture has initiated decay.

No matter what kind of wiggly passenger you see on firewood, never treat it with insecticide. Burning insecticide-treated wood poses a real health risk to those in the home.

The key to critter prevention is this: If they’re not in your firewood, they’re not getting inside. And they only like firewood if it’s damp. Seasoned wood that’s been stored off the ground and out of the weather is unlikely to harbor insects. Keeping firewood out of garages and basements is highly recommended — ideally it should be stored away from the house in a non-attached structure on pallets or a dry floor.

If you cut your own wood, timing can help. Trees cut between late autumn and early spring, especially if the wood is split right away, are less likely to garner wood-boring insect eggs. However, even if insects get a start, they’ll perish when the wood is fully dry.

Even if adjusting the “thermostat” involves a trip to the woodpile, I think wood heat is great. It’s economical, sustainable and keeps you in shape, not to mention that nothing feels as good as a seat by the woodstove on a sub-zero night. What’s not to like about heating with wood?

Wait — never mind.

Photo, from above:wood pile courtesy Wikimedia user Chmee2; and Asian longhorn beetle larvae courtesy USDA.