Spread of ash borer in Minnesota slower than expected

  • Article by: BILL MCAULIFFE , Star Tribune
  • Updated: April 24, 2012 - 10:58 PM

Aggressive treatment may have paid off, monitors say.

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Adult borers are expected to emerge as soon as next week.

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On the eve of the emerald ash borer's annual emergence, the state's top bug monitors are encouraged that the spread of the tree-killing pest has been relatively slow, particularly in the metro area.

"I think the reason for that is the work that's been done," said Mark Abrahamson, entomologist for the Minnesota Department of Agriculture. He said that several public agencies in the metro area have worked to identify suspected infestations, remove infested trees, thin the ash tree population and even treat some trees with insecticide.

"You've always got to keep your guard up. It could show up anywhere else," Abrahamson added. "But more and more, what I'm hearing is a more optimistic outlook, like maybe there is something we can do -- rather than gloom and doom."

Adult ash borers are expected to emerge from under the bark of ash trees they've infested perhaps as soon as next week -- about three weeks earlier than normal, Abrahamson said.

St. Paul has removed nearly 3,000 ash trees since May 9, 2009, when the borers were detected in the city's St. Anthony neighborhood. Minneapolis has removed about 2,400 trees since 2010, when the beetles were found in Prospect Park, about a mile southwest of the St. Paul site. A recent study of trees within about 2 1/2 miles of the initial detection site in St. Paul found 20 of 300 sampled trees to be infested. Geir Friisoe, director of the state Agriculture Department's plant protection division, said that was far fewer than researchers expected, as was the number of beetles.

Shawn Bernick, director of research for Rainbow Tree Care Scientific, said the Agriculture Department's recent study "suggests we have more time" to fend off ash borers. But he cautioned that Minnesota might not be immune to the experience of other states, where ash borer numbers exploded after a period of low activity.

The company is working with metro-area cities to launch an awareness program that might involve ribbons to identify ash trees, with informational cards attached describing the trees' ecological and commercial value, and strategies to deal with ash borers. That effort could begin in May.

Bill McAuliffe • 612-673-7646

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