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Invasive insects in imported furniture may be threat to Minnesota, Wisconsin forests

The burrowing larvae of a velvet longhorned beetle was found in rustic log furniture imported from China. State insect experts are asking people who may have purchased imported log furniture to check for inspect damage and report any findings of insects. Photo courtesy of the Minnesota Department of Agriculture1 / 3
Insects that burrowed into trees in China got a free ride to Minnesota when untreated logs were made into rustic furniture and shipped to the U.S. Insect experts are worried that, if the bugs escape into the wild, they could wreak havoc on Minnesota trees. (Photo courtesy Minnesota Department of Agriculture)2 / 3
The paths of burrowing insects on this piece of rustic log furniture can easily be seen when the bark is removed or falls off. Insect experts have confirmed multiple pieces of rustic log furniture imported from China to Minnesota and Wisconsin were infested with invasive insects. Photo courtesy of Minnesota Department of Agriculture3 / 3

Rustic log furniture imported from China into Minnesota and Wisconsin has been found to be infested with invasive insects that could damage native trees.

Both states’ agriculture departments on Tuesday confirmed multiple incidents of two different species of Chinese bugs hitchhiking on rustic, whole-log furniture in 2016.

The brown fir beetle was found in rustic pine log furniture imported from China, while the velvet longhorned beetle was discovered in rustic walnut log furniture, wrongly described as hickory, also from China.

“We’ve had invasive insects imported into the state in other material, but this is pretty much a first with furniture,” Mark Abrahamson, an entomologist with the Minnesota Department of Agriculture, told the News Tribune.

The problem appears to be that the log furniture was never properly treated before being shipped from China, Abrahamson said. Insects are unlikely to survive in treated lumber, boards or composite wood. But untreated whole logs are the perfect long-distance travel mode for the wood-boring beetles that can live for up to two years in the furniture.

Some consumers had the furniture in their homes for more than a year before noticing damage caused by the burrowing insects, Abrahamson said.

Officials say it’s possible that some infested furniture still has not been located.

The brown fir beetle was found in furniture purchased online in 40 different states, leading to a national effort by the U.S. Department of Agriculture to track down the buyers — with hundreds. perhaps thousands of pieces of furniture potentially carrying the bug.

“Multiple pieces in Minnesota were found to be infested,” Abrahamson said. “Once people were notified, they saw the damage.”

The larvae of a velvet longhorned beetle was found in log furniture imported from China. (Photo via MN Dept. of Agriculture)The importing company cooperated and recalled the furniture. Authorities made sure it was properly destroyed, and most consumers received a refund, Abrahamson said.

The velvet longhorned beetle was found in furniture purchased in Minnesota and Wisconsin but sold through multiple retailers, making it harder to round up all the potentially infested furniture.

“It’s been tables, chairs, dressers, beds,” Abrahamson said. “We’re not sure how far out people who bought this type of furniture in Minnesota took it to their cabins or whatever.”

USDA officials now are working to expand their authority to regulate log furniture as a potential high-risk invasive species pathway.

Both bug species have been found in multiple species of trees, making them potentially dangerous to Minnesota and Wisconsin forests and urban trees. The brown fir beetle is believed to be a warmer-weather species and probably not as big a threat in the Northland. But the velvet longhorned beetle can withstand colder weather and already has been found on some wild trees in Minnesota, Abrahamson said, and appears to be able to live in many species of trees.

“We don't know if they are established here or if it’s just isolated. We are really working on that one right now. We think that’s the one of more concern,” Abrahamson said.

If the insects worked their way out of the furniture and made it outdoors, “they could pose a real threat to our forests, crops and wood products industries,” said Brian Kuhn, director of the Plant Industry Bureau in the Wisconsin Department of Agriculture, Trade and Consumer Protection.

The bugs aren't a threat to people but, if they escape, could begin to damage urban and forest trees much like the emerald ash borer, also a Chinese import believed to have arrived in Michigan via wooden packing crates more than a decade ago. That insect has since spread, mostly by people moving wood, to dozens of state and provinces and has killed millions of ash trees.

Like the emerald ash borer, the two new bugs start in the worm-like larval life stage, feeding under the bark and causing internal damage to trees. They emerge as adults to disperse and then lay more eggs on the bark of other trees. The eggs hatch, and the new larvae burrow under the bark to start the cycle again.

“This is a good reminder that invasive insects, which can do great harm to Minnesota’s natural resources, can get into the state in many ways,” said Geir Friisoe, director of the Minnesota Department of Agriculture's Plant Protection Division, in a statement.

Rustic log furniture made in Minnesota or Wisconsin might be carrying insects, but they probably are native bugs and not a major concern. State officials said “buying local is always best,” while also making sure the furniture comes from a reputable source.

Consumers who have rustic log furniture which was manufactured outside the U.S. should look for several signs of insect infestation:

  • Sawdust around the furniture, a sign that insects are active in the wood.
  • Visible exit holes, especially small, round tunnels that suggest insects were in the furniture and have burrowed their way out.
  • Damage to the wood, such as loose bark with tunneling underneath, indicating the wood was infested at some time.

In Minnesota, consumers who suspect they have purchased infested furniture should contact the state’s Arrest the Pest line at (888) 545-6684 or arrest.the.pest@state.mn.us. In Wisconsin, e-mail shahla.werner@wi.gov or call (608) 224-4573.

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