It's the first cold night of the year, so you carry an armload of oak in from the back fence and stack it by the hearth. Three days later there are beetles on the windowsill, a wasp bumping the lamp and a spider walking across the rug. None of them came through the door. They rode in on the wood.
Firewood is a natural shelter for insects, and a warm living room tells them spring has arrived. The fix is mostly about where you stack the wood, how you stack it and how much you bring inside at once.
Keep firewood outside, off the ground and away from the house, and bring in only what you'll burn in a day or two. University of Illinois Extension advises stacking wood at least 3 feet from any building. Knock logs together and check them before carrying them in, and never spray firewood with insecticide, because burning it can release harmful fumes.
What Bugs Live in Firewood?
Two groups of insects turn up in a woodpile, and only one of them actually lives in the wood.
Wood borers and wood users. These were usually in the tree before it was cut. Wood-boring beetles lay eggs in dying, freshly cut or recently killed trees, so the larvae are often already inside when the log reaches your yard. University of Illinois Extension lists the usual suspects:
- Longhorned beetles (family Cerambycidae), probably the most common borer in firewood. Adults run from about 1/4 inch to 2 inches long; the larvae are whitish, legless grubs.
- Metallic wood-boring beetles (family Buprestidae), flattened and bullet-shaped, often with a metallic sheen. Their larvae are called flatheaded borers.
- Bark beetles, under 1/8 inch, brown or black and cylindrical.
- Carpenter ants (Camponotus species), which nest in damp, rotting wood but don't eat it.
- Subterranean termites, which live in the soil and tunnel up into wood stacked on the ground.
Squatters. These just use the stack as a dry, dark place to spend the winter. University of Florida entomologists list earwigs, centipedes, millipedes, beetles, cockroaches, stink bugs, scorpions and spiders. The University of Kentucky adds overwintering wasp and hornet queens, praying mantis egg cases and moth cocoons.
Some wood-boring larvae spend a year or more tunneling before they become adults, so a log can produce beetles long after it was split.
Can Firewood Bugs Infest Your House?
Mostly no, and that's the good news. Clemson Extension entomologist Eric Benson describes the insects that emerge from firewood as nuisance pests that should not infest furniture or structural wood. The University of Kentucky rates borers' potential to infest a home's framing as very low: they favor certain woods like oak and hickory and need more moisture than the dry lumber in your walls. Illinois Extension puts it plainly: indoor wood is too dry for them.
A carpenter ant or a few termite workers carried inside on a log won't start an infestation either. The real risk is outside. A pile that sits against the house for months, or right on the soil, can feed a termite colony or host a carpenter ant nest that later moves into damp wood in your siding, porch or sill plate. If you're seeing winged insects and aren't sure which one you have, our guide to carpenter ants vs. termites covers the differences.
The other real hazard is to you. Clemson's Home & Garden Information Center says widow spiders are most commonly found outdoors in woodpiles. South Carolina has the southern black widow (Latrodectus mactans) statewide, the northern black widow (L. variolus) mainly in the Piedmont and Upstate, and the brown widow (L. geometricus), which is thickest along the coast. Wear gloves when you pull wood off the stack. See are black widows common in Charleston? for what they look like.
Where Should You Store Firewood?
The extension guidance from Illinois, Kentucky and Florida lines up on the basics:
- Away from the house. Illinois Extension recommends at least 3 feet from homes, garages, sheds and other buildings. Farther is better if your yard allows it. Kentucky specifically warns against stacking wood in or against the house for long periods.
- Off the ground. A metal rack, pallets or a row of concrete blocks keeps the bottom logs out of the soil, which deters termites and helps the wood dry. Wood left on damp ground is what carpenter ants look for.
- Air on the sides, cover on top. Florida entomologists point out that good air circulation dries wood faster. Kentucky suggests covering the pile during summer and fall. A tarp over the top with the sides left open does both.
- Oldest wood first. Burn the oldest wood first and don't stack fresh wood on top of old, per Kentucky. Old wood at the bottom of a pile is where nests settle in.
- Not in a sheltered corner. Florida's Robert Annis notes that stacked wood in a sheltered spot is free lodging for rodents. Keep the pile in the open, not behind the shed or under the deck.
UF/IFAS also recommends splitting and stacking wood in the fall, since seasoned wood is less attractive to insects come spring. In the Lowcountry and Hampton Roads, where humidity keeps wood damp longer, an open-sided stack with a covered top earns its keep.
How to Bring Firewood Inside Without the Bugs
Cold keeps insects in the wood quiet. Warmth wakes them. Illinois Extension notes that the longer wood stays inside, the more likely its residents are to emerge, which is why the advice everywhere is the same: bring in a day or two of wood at a time.
- Knock it first. Kentucky recommends shaking, jarring or knocking logs together before you carry them in, and brushing off webbing and cocoons.
- Look at each piece. Check for holes, sawdust, ants, egg cases or spiders. A log riddled with fresh holes can go in the fire pit outside.
- Skip the garage stockpile. A big stack in an attached garage is a woodpile against the house with a roof on it.
If something crawls out anyway, don't reach for a spray. Clemson suggests taking the wood back outside and removing the insects by hand, vacuum or broom. Kentucky notes that these shelter seekers can't survive for long indoors and won't multiply.
Should You Spray Firewood With Insecticide?
No. Every extension source we checked says the same thing. Kentucky calls it unnecessary and potentially dangerous because of fumes produced when the treated wood burns. Illinois adds that a spray won't reach insects already inside the wood anyway. If a piece is badly infested, UF/IFAS says to discard it or burn it outside in a fire pit.
Buy Local and Don't Move Firewood
This one is about forests, not your living room. Clemson forest health specialist David Coyle says moving firewood long distances is one of the most common ways invasive forest pests spread. Illinois Extension points to the emerald ash borer (Agrilus planipennis), an invasive beetle of ash trees, as one pest that moving firewood has helped spread. Get firewood close to where you'll burn it, and if you buy packaged wood, choose wood that's been heat-treated. Don't Move Firewood gives the same advice for camping trips.
When to Call a Professional
- You find mud tubes running up the foundation or onto the woodpile near the house
- Winged insects show up indoors in spring, away from the hearth
- Large black ants keep appearing inside, or you find piles of coarse sawdust
- The ground where an old woodpile sat shows damaged wood, or it sat against the siding for years
Termites and carpenter ants found in a woodpile are a reason to look at the house itself. You can start with our guide on how to check for termites yourself, and our fall pest-proofing checklist covers the other gaps that let overwintering pests in. For an inspection, see our termite control and ant control services, or request a quote for Charleston, Columbia, Greenville/Spartanburg, the Raleigh area or Hampton Roads.
Key Takeaways
- Stack it away from the house: at least 3 feet from any building, per University of Illinois Extension, and never against the siding.
- Get it off the ground on a rack, pallets or blocks to discourage termites and carpenter ants and help the wood dry.
- Bring in a day or two's worth at a time. Warm wood wakes up whatever is living in it.
- Most firewood insects are nuisances, not a threat to your framing. The bigger risk is a pile that feeds termites or carpenter ants next to the house.
- Never spray firewood. Treated wood can give off harmful fumes when burned.
- Wear gloves. Widow spiders are commonly found in woodpiles.
Sources: K. Johnson, "Why are there bugs in my firewood? Identifying and managing firewood insects", University of Illinois Extension, 2022; L. Townsend, "Firewood Insects" (ENTFACT-626), University of Kentucky; R. Annis, "Keeping Pests Out of Firewood", University of Florida IFAS Entomology and Nematology, 2023; D. Attaway, "Don't bring uninvited holiday guests inside with Christmas trees or firewood", Clemson University, 2022; Clemson Home & Garden Information Center, "Widow Spiders"; The Nature Conservancy, Don't Move Firewood.
Frequently Asked Questions
Mostly wood-boring beetles such as longhorned beetles, metallic wood-boring beetles and bark beetles, plus carpenter ants and termite workers. Overwintering squatters also hide in the stack, including spiders, centipedes, earwigs, cockroaches, stink bugs and wasp queens.
Rarely. Clemson and University of Kentucky entomologists say wood borers from firewood should not infest furniture or structural wood, which is too dry for them. The bigger risk is a woodpile stacked against the house or on the soil, which can support termites or carpenter ants next to the structure.
University of Illinois Extension recommends stacking firewood at least 3 feet from homes, garages, sheds and other buildings. Farther is better if you have the room, and the pile should never lean against siding.
Only what you'll burn in a day or two. Insects in the wood become active as it warms up indoors, so the longer it sits inside, the more likely bugs are to emerge.
No. Extension entomologists advise against treating firewood with insecticides because burning treated wood can produce harmful fumes, and sprays don't reach insects inside the wood anyway.
Firewood stacked directly on the ground can be tunneled into by subterranean termites from the soil, and damp wood attracts carpenter ants. Keeping the pile on a rack or pallets and away from the house reduces that risk.
A small amount for the next day or two is fine, but a large stockpile in an attached garage is the same as a woodpile against the house. Keep the main supply outside, off the ground and away from buildings.
Photo credits: Photo: Julian Kraus on Unsplash; Nwbeeson, CC BY-SA 4.0, via Wikimedia Commons; Photo: andre govia on Unsplash.