They eventually kill off their arboreal hosts by disrupting their "circulatory systems," experts say.
"So far, it's been an urban problem," said Michael Bohne of the USDA Forest Service in Durham, New Hampshire.
"But if you look at an aerial image of the forests surrounding Worcester, you'll see that once you are just a few miles out of town you're in a forested area," he said.
"[It's] a closed canopy hardwood forest almost to the [northern boundary of] Canada."
The Worcester beetles hitchhiked into the U.S. from China via infested wooden packing materials, including crates and pallets.
Despite restrictions to prevent the entry of untreated wood, port officials continue to intercept it in warehouses across the country.
(Related: "Alien Beetles Tracked with "Ray Guns," Dental Floss" [October 16, 2006].)
Catching it Early
In some cases, officials have been able to halt the slow-moving species' spread by catching infestations early.
In Worcester, officials are planning to cut down infested trees and those at high risk of attack, said Markham of the beetle-eradication program.
Other trees will be treated with chemicals to kill off the pests, she said.
(Related: "Invasive Bugs, Plants Prefer Summer Plane Flights, Study Finds" [April 11, 2007].)
With the immediate threat under control, federal and local experts are doing some detective work to see if the beetles had expanded beyond Worcester.
The experts are talking to tree-care companies and others who handle trees to see if wood from the quarantined area might have been transported to other locations.
Sun Seeker
The beetle is native to Korea, where it is rare, and also to China, where it wasn't considered a pest until about half a century ago.
In the 1950s and '60s the [Chinese] government started importing non-native, fast-growing European trees to use as wind breaks because [China has] an expanding desertification and dust storm problem, said Michael Smith, an entomologist with USDAs Agricultural Research Service in Newark, Delaware.
Smith has studied the beetle for over a decade in China and the U.S.
In China we would say its an induced pest, because they brought in millions of non-native trees and planted them in large areas of only a few species.
The beetles tend to favor sunlit areas and may not thrive deep in forests with a high diversity of tree species, Smith added.
"We've learned over time in China that it's really an edge attacker.
"It starts at the edge and over time will very slowly move into a large plantation with a closed canopy area."
Tree Heritage
Such behavior suggests the beetle could remain a greater threat to trees in urban and suburban areas.
But University of Vermont entomologist Margaret Skinner stressed that no one knows how the beetle might fare in New England's rural forests.
And with all that's at stake, no one wants to find out.
"With maple syrup and the foliage season, we're talking potentially millions and millions of dollars [of damage]," she said.
"Every third tree in Vermont is a maple tree of some sort. We really care about our maple trees. They are part of our heritage."
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