As the air turns crisp, you may want to take refuge in front of a roaring fire. But if, like a lot of people, you don’t happen to have a forest out back, be careful when buying a bundle or two of firewood from a retailer. According to a new study, the odds are pretty good that your firewood could become the source of a very unwelcome kind of beetlemania.

Researchers from Colorado State University and Northern Arizona University bought 419 bundles of firewood from grocery stores, big box stores and gas stations in Colorado, New Mexico, Utah and Wyoming. They put the firewood bundles in insect cages to see what would emerge.

Over the next 18 months, 47 percent of the bundles yielded insects, most emerging within 200 days of purchase, according to their paper in the Journal of Economic Entomology.

On average, the researchers saw 11 insects come out of each bundle, but one bundle yielded 520 bugs. Pine, fir and mixed conifer wood bundles seemed to yield the most live insects.

Overall, the team found live insects from over 85 different families, most of which were different kinds of beetles. The researchers did not find the Asian longhorned beetle or the emerald ash borer, which are two of the more destructive invasive species recently introduced to the U.S. But it is highly feasible for those species to hitch a ride on a cord of firewood bound for your local Wal-Mart or gas station, the scientists pointed out.

The team's findings point to firewood as a potentially dangerous vector for invasive insects to move vast distances.

“Sources of retail firewood are not always local because demand may exceed local supply and large retail chains may have supplies from distant states,” the authors wrote.

As the researchers found, the bugs can inhabit wood for a long time before emerging – long enough for firewood to be shipped far away from its source and introduce ravenous beetles to new forests.

While some state and federal agencies are placing restrictions on moving firewood too far from its origin, what might be even more effective is requiring retail firewood to be heat-treated before it is shipped, the authors argue.

“Pretreating firewood before it is shipped so that insects or pathogens are killed would be the prudent choice and would not restrict firewood commerce as much as bans on firewood movement across state borders,” the authors wrote.

SOURCE: Jacobi et al. “Retail Firewood Can Transport Live Tree Pests.” Journal of Economic Entomology 105: 1645-1658, 8 October 2012.

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