City continues treatment, removal program

Newly identified infestations of emerald ash borer have pushed the deadly tree insect closer to Burnsville, where efforts are already underway to treat healthy ash trees on public property and remove unhealthy ones.

An infestation was confirmed Dec. 23 in Lebanon Hills Regional Park in Eagan, just north of the border with Apple Valley.

An even closer infestation was confirmed Nov. 7 in Bloomington. The location is about a mile north of the Black Dog power plant in the Minnesota River Valley in Burnsville, said Terry Schultz, the city’s parks, recreation and natural resources director.

“It’s coming at us from two sides now,” Schultz said. “Being part of the Minnesota River valley, I’ve always expected it will migrate through the river valley. It jumped a little bit when they found it in Lebanon Hills.”

EAB had already been found in St. Paul and at Fort Snelling. Its arrival has been long anticipated in Burnsville, where the city has been ratcheting up spending to fight the disease.

“It is likely here; we just haven’t found it yet,” Schultz said.

A total of $200,000 is budgeted this year, and $50,000 annual increases are planned through 2019, when spending would reach $400,000, Schultz said. The city wrote its first EAB-containment plan in 2010.

“There is, as far as I’ve seen, no way of stopping it,” Schultz said. “It’s 100 percent mortality for trees that aren’t treated.”

The city revised its plan in 2013, putting more emphasis on treatment and less on removal. Treatment appears to have a good track record in healthy trees and has come down in cost, Schultz said.

Beginning work last year, a city-hired contractor treated 478 of 2,900 trees targeted for treatment and removed 100 of the 1,100 targeted for removal, Schultz said. The targeted trees are in medians and on public right-of-way (15 feet back from the curb) and in active-use areas of city parks.

Plans call for completing the treatments in 2016 and the removals in 2017, Schultz said. The treatments will then continue every two years, he said.

The targeted trees are largely in the eastern part of Burnsville, particularly the North River Hills area in the northeast part of the city, Schultz said. Treatments and removal will work their way south as efforts continue, he said.

Many more ash trees are in city park woodlands (an estimated 14,300) and on private property (an estimated 22,600).

“For now, we’re encouraging folks that want to save their ash trees that are in good condition to go ahead and treat them at their own cost,” Schultz said. An ash tree that hasn’t lost more than 25 or 30 percent of its leaf canopy is probably healthy enough to be saved, he said.

The city will continue the practice begun last year of offering property owners the same treatment cost it gets through its contractor, he said. Treatment is through injection of a pesticide called TREE-age (pronounced “Triage”).

The city has the authority to tag trees on private property and compel their owners to remove them. Public safety problems could trigger that, Schultz said; when trees have died of EAB, they become very brittle and fall easily.

“I don’t speculate we’ll have to use that authority a lot, at least I hope not,” said Schultz, who expects that property owners would want to remove the hazardous trees.

In public park woodlands, the city may do  targeted treatments to halt infestations, but treating all 14,300 trees isn’t practical, according to Schultz.

“In those natural areas you just kind of have to let nature take its course,” he said. “They will reforest over time.”

Burnsville’s total ash tree population, public and private, is estimated at 40,885 — 19 percent of its 220,120 trees. The counts are taken from city inventories and tree surveys.

“It was a very popular tree when Burnsville was developing a lot of housing,” Schultz said.

The spread of infestation is a process that “grows exponentially at some point,” he said. After five or six years, it’s difficult to contain, Schultz said.

“We aren’t to that point in the metropolitan area,” he said. “We’re still trying to remove trees as quickly as we can find them and split it. We will get to that point at some time. That’s what we’ve seen in other states. Minnesota’s done a much better job of keeping it under control initially and kind of slowing it down.”

Information on the city’s EAB plan is at www.burnsville.org/index.aspx?NID=905.

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