Emerald ash borer larvae make S-shaped tunnels. Submitted photo: Jeff Hahn
Emerald ash borer fast facts
Method of killing: Larvae feed on a tree's nutrients under the bark.
Speed of spread: A couple miles per year by themselves. Hundreds or thousands of miles in wood transported by people.
How did they get here: The non-native insect was likely first introduced in 2002 in the Detroit and Windsor, Ontario area.
Ash trees in Minnesota: More than 900 million.
Ash trees along Hopkins streets: 9,954 with 3.8 ash trees per acre, which make up 10 percent of the trees there.
What about my apple tree? Emerald ash borer only attack ash trees. There are three common varieties in Minnesota - black ash, green ash and white ash - and all three are susceptible to infestation.
Signs of infection include: Die-back of leaves in the upper one-third of the tree's branches, heavy woodpecker activity, D-shaped exit holes in the bark and S-shaped tunnels under the bark.
Who will pay for tree removal? State officials anticipate federal funding, but there is limited funding available at the state level. Local units of government and individual property owners should prepare for the possibility of covering a substantial portion of the costs.
Sources: Minnesota Department of Agriculture, Minnesota Department of Natural Resources, University of Minnesota Extention
By David Schueller
There's still mourning in the voices of some who remember how Dutch elm disease destroyed the arching elm tree canopies of neighborhood streets.
Ash trees - hardy and readily available - often replaced elms. Minnesota has more than 900 million of them.
"The new elm was the ash, because it was cheap, and it grew everywhere," said Paul Buck, city forester for Plymouth.
The emerald ash borer, then, is the new Dutch elm disease, except the effects of the ash-killing insect are more difficult to detect.
In the Lake Minnetonka area, foresters have been busy after learning of a confirmed infestation in St. Paul in May.
So far, there have been no confirmed finds of the insect in Lake Minnetonka cities. Although their spread west is probably inevitable, it can be slowed.
In Plymouth, Minnetonka and Hopkins, foresters said they don't yet have concrete plans on how to deal with the threat of infestation.
But, like homeowners, cities are beginning to sort through options.
"I think we're just barely passed denial," said Buck. "We all just thought, it's not here. Now we're like, I'm really mad it's here."
Buck said the city will have to decide how many trees it's willing to take down, whether it will treat trees with pesticides, and whether waiting to see how bad it gets is still an option.
They're similar questions to those homeowners are facing.
Like other city foresters, he's getting inundated with calls about emerald ash borer.
Emily Barbeau, Minnetonka city forester, said that even before learning of the infestation, the city took precautions.
When considering development plans, it
hasn't allowed ash to be planted.
And, in part through its annual tree sale, the city has encouraged a diversity of species to be planted on private properties.
The city knew the pest was out there.
"We just didn't think it would come this quickly," Barbeau said.
Barbeau and others warn against cutting down healthy ash trees, which could only hasten the infestation.
"People shouldn't panic. This pest has been in St. Paul they think for up to four years. And so panicking is not going to help the situation," Barbeau said.
She frequently hears from people who've found look-alike beetles - some bring them in for inspection - or are worried about injured ash trees.
There are even those looking to make money off people's fears, she said.
"I've noticed a proliferation of fly-by-night companies going door to door scaring people into thinking they have to remove their ash trees," Barbeau said.
Because of Minnetonka's distance from the infestation, she said, now is the time to think about whether to invest in pesticides to prevent infestation. Pesticide treatment can cost between $50 and $200 per year, per tree.
Ray Vogtman, Hopkins' superintendent of streets and parks, said the threat is on the horizon, but said state agencies will have a role to play as to how cities deal with the problem.
As for removing trees, he compared the problem to Dutch elm disease.
"It can kill a lot of trees in an area once it arrives. Unfortunately, like Dutch elm disease, it's a long process," Vogtman said.
Ken Holman, community forestry coordinator with the Department of Natural Resources (DNR), said communities should know that by slowing the spread, they'll be able to pay the cost of removing trees over a longer period of time.
"We want to minimize the impact of the bug. And it's going to be pretty disasterous," Holman said.
Cities will need to revise ordinances to have the authority to implement a pest management program, similar to the days of dealing with Dutch elm disease, he said.
Such ordinances could allow cities to enter property and survey and condemn and remove trees if a homeowner doesn't.
Michael Schommer, communications director with the Minnesota Department of Agriculture (MDA), compared emerald ash borer to Eurasian water milfoil. Like the invasive aquatic species, the emerald ash borer's spread can be slowed.
"This is a similar situation, where you've got a pest or a plant that might move really slowly on its own, but when people help it spread it can jump to new areas," Schommer said.
The insect is native to eastern Asia. After likely being introduced in 2002 in the Detroit and Windsor, Ontario area, it spread to the U.S. and Canada. But it was only as close as Chicago as of last year, Schommer said.
People helped it get here.
Minnesota has the second highest number of ash trees out of any state, he said.
"We've got a lot on the line," Schommer said.
The MDA put an emergency quarantine on Hennepin and Ramsey counties in May, which makes it illegal to transport firewood out of the two counties.
Because emerald ash borer larvae tunnel into a tree and feed on its nutrients under the bark, it would be easy to unknowingly transport infected firewood. When mature, the beetles chew their way out of the bark.
And even though the confirmed infestation is limited to St. Paul, the emerald ash borer could be elsewhere.
"It could already be here, it could be in Plymouth and we wouldn't know it. It really could be anywhere," Buck said. "And at some point somebody's going to come across a tree that's so impacted that they'll peel back the bark and say, 'Oh, it's here.'"
Reader Comments
Posted: Tuesday, June 16, 2009
Article comment by:
Mark Broin
After years of experiencing the expenditure of millions of dollars of taxpayer dollars, significant amounts of property owner dollars, and unknown hours of wasted civil servant time to unsuccessfully stop the spread of Dutch Elm disease, why would citizens allow the spending of one more nickel to “slow” the inevitable spread of emerald ash borer infestation? It seems to me the natural end should be allowed to progress as quickly and cost effectively as possible. Please, in this economic environment, spend public money and expend public resources in manner which gives due respect to the principles of common sense.
