By Dan Linehan

MANKATO — Click here to see a map of Mankato's ash tree concentration.

If the metallic-green insects are coming for the 2,400 or so ash trees along Mankato’s boulevards, should the city beat them to the punch and start taking down the most bedraggled-looking ash first?

Mankato’s City Council is considering replacing and removing the ash along public roads over many years rather than face the prospect of all of them dying over a few years from an emerald ash borer infestation.

The $1.35 million price tag is daunting, though. It costs about $400 per tree for removal, and about a third of that to replant another tree. The city hasn’t counted ash trees in parks or on private property, though ash trees make up about a fourth of the city’s boulevard trees.

Councilman Vance Stuehrenberg said he thinks there’s an ash in his front lawn, and his hilltop neighborhood is thick with the trees, according to the city’s tree map.

“There is such a beautiful canopy of trees on East Main Street,” he said.

Hagberg also said no ash trees have been planted in the past three years because there were too many of the trees already. Species diversity was a goal even before the ash borers, which are native to China.

City Forester Brian Hagberg told the council preventive measures aren’t worth the money, as there’s no known way to stop the bugs.

Stuehrenberg said ash borers are just one of the things you can’t control.

“One year, it’s gonna hit Mankato, and we just have to take the best precautions we can,” he said.

Hagberg said a resident called recently with worries that ash borers have infested his trees.

Turns out it was a maple.

“Everything right now that’s gonna be wrong with a tree is emerald ash borer,” Hagberg said sarcastically. There are plenty of tree diseases, including for ash, that present similar symptoms.

North Mankato hasn’t addressed the issue yet, Public Works Director Rich Peterson said.

“We could get quite a few years outta those trees before we take ’em down,” he said.

Ash borer warning signs include a dieback in the leafy area near the tops of trees, a D-shaped exit hole about a quarter-inch in size and small shoots sprouting along the base of the tree, said Michael Schommer, a spokesman for the Minnesota Department of Agriculture.

Those who think they have an ash borer can call the agriculture department’s “Arrest the Pest” hotline at 651-201-6684. The department’s Web site, www.mda.state.mn.us, has a plethora of information about how to identify ash trees and ash borers.

The city of Mankato hasn’t taken formal action on a policy to start culling the city’s ash — the least healthy ones would go first — but it is considering making it illegal to bring firewood to Land of Memories Park.

Hagberg said the bugs can travel about 15 miles a year left to their own devices but can travel much longer distances inside firewood. The state has long encouraged campers to burn firewood bought or culled at the site rather than carry it long distances.