As you stock up on firewood for chilly winter days, do you pay much attention to where the wood comes from?

Some people head out into the woods, cutting firewood from trees that have already fallen and started to cure. Others buy from roadside stands or even the grocery store. It's possible you might have no idea if the wood you're chucking into your fireplace or stove came from a few miles away or across the country.

Firewood can be a pathway for invasive insects and diseases. So if it's transported far away from where the original tree once grew, it can spread those pests and pathogens to new locations.

The emerald ash borer— a beetle that got here from Asia in shipping crates and pallets made of infested wood — has killed tens of millions of ash trees in North America since its discovery here in 2002. The redbay ambrosia beetle, which causes laurel wilt disease, is marching through Georgia and Florida.

"You have the same problem of invasive species everywhere, but you have different species in each region of the country," says Leigh Greenwood, the Don't Move Firewood campaign manager with The Nature Conservancy.

Native forest ecosystems have complex checks and balances that combat native insect populations and plant diseases. Imported bugs are often resistant to these natural controls, causing greater harm than native pests. And the destructive insects and diseases often hitch a ride on firewood, speeding the spread of the devastation.

The emerald ash borer flies further on its own that most beetles, says Greenwood, but still moves just two or three miles a year.

"But when you move firewood, it can move hundreds of miles in a day," she says.

The importance of staying local

Look for firewood that has state or USDA certification. Look for firewood that has state or USDA certification. (Photo: Don't Move Firewood)

The Don't Move Firewood campaign recommends trying to use firewood that comes from 10 miles away or less. Fifty miles should be the absolute limit.

If you're camping and are allowed to collect wood locally, that's an ideal situation since you know your source. If you're buying wood for home use, ask the seller if he's the one who collected it and where it came from, Greenwood suggests.

Often, you might just buy a packaged stack of heat-treated firewood from a store. In those cases, it should have a label that tells where it was collected. Look for a United States Department of Agriculture (USDA) APHIS heat-treatment seal or state certification seal. If it says it was "kiln-dried," that doesn't guarantee the wood was heated long enough or hot enough to kill any potential pests, Greenwood says.

If a tree falls on your own property, it's great to use it in your own fire pit or fireplace or give it to the neighbor down the street.

"The key is to keep it local," Greenwood says. "Don't haul it with you on vacation. Don't give it to somebody who is going to bring it to them to their cabin two states away."

Looking for issues

lanternfly egg mass on a tree in Pennsylvania Lanternfly egg masses are not always this obvious. (Photo: U.S. Department of Agriculture [public domain]/Flickr)

Don't assume you'll be able to spot problems in firewood.

"A tree killed three years ago may look dead on the outside, but it's teeming with life on the inside," writes David Coyle, assistant professor in the Department of Forestry and Environmental Conservation at Clemson University.

Even an expert might not be able to see a few tiny insect eggs or microscopic fungus spores hidden in a stack of wood.

"Some of these things are literally too small to see and others are just incredibly clever," says Greenwood, pointing out how spotted lanternflies are well camouflaged as they climb aboard lumber to hitchhike their way into other states. "There's no realistic way to visually inspect or know that your firewood is safe to move."

And don't think burning all the wood in the campfire will prevent the spread of insects or fungi.

"Even a small chip of bark containing invasive insect larvae can fall unnoticed to the ground," says James Johnson of the Georgia Forestry Commission. "A sudden rainstorm can wash fungus spores off wood or out of your pickup, so the danger is very real."

Editor's note: This story has been updated with new information since it was originally published in July 2012.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

Why buying local firewood matters
Invasive insects and diseases can hitch a ride on firewood — with devastating effects on local ecosystems.