EAST LANSING, Mich. New research at Michigan State University shows that the uber-destructive emerald ash borer arrived at least 10 years before it was first identified in North America.
The study, published in the current issue of journal Diversity and Distributions, shows that EABs were feasting on ash trees in southeast Michigan by the early 1990s, well before this pest was discovered in 2002, said Deb McCullough, MSU professor of forest entomology.
"We suspect they arrived inside wood crating or pallets imported from Asia where the beetle is native," she said. "There were probably only a few live beetles that arrived, but ash trees are common in urban landscapes as well as in forests. When they emerged, there were likely ash trees nearby, providing food for the beetles and their offspring."
Slender cores were collected from the trunk of more than 1,000 ash trees across six counties in southeast Michigan. By studying the tree rings on each core and identifying key "marker" years, the team was able to determine the year each tree was killed by emerald ash borers. This study, which encompassed more than 5,800 square miles, is by far the largest area sampled with tree rings. In addition, this was the first study to use tree rings to track the spread of an invasive tree-feeding insect.
The scientists found ash trees were killed as early as 1997. Since it takes many years before the beetle population was large enough to kill ash trees, the team concluded that the invasive species had been in southeast Michigan since 1992 or 1993 and perhaps even earlier.
Emerald ash borers now have infested at least 22 states and two Canadian provinces and have become the most destructive and costly forest insect to ever invade North America, McCullough said.
"Emerald ash borers are killing trees so fast across such a large geographic area, that nobody actually knows how many trees are dead," she said. "We do kn
|Contact: Layne Cameron|
Michigan State University