Blaine chops ash trees to prevent emerald ash borers

Article by: BRYNA GODARSPECIAL TO THE STAR TRIBUNE
Updated: July 24, 2012 - 12:15 PM

The city has replaced nearly 550 mature ash trees with a variety of new trees in the past two years.

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An adult emerald ash borer

Photo: , Associated Press

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Across Minnesota, cities and agencies are working to halt the spread of the emerald ash borer. Blaine's plan has been to get to the ash trees before the pest does.

Over the past two years, the city has removed 596 trees from parks and boulevards, exceeding its goal of 200 per year, and planted about 545 replacements of different kinds.

Officials' concern is that if the ash borer infiltrates Blaine, it could spread quickly. Their hope is that, by gradually taking out ash trees and putting in new species, they can avoid incurring a big replacement tab in any single year.

"We're trying to spread out the cost of a problem over many years," said park supervisor and city forester Marc Shippee.

Tree removal is not mandatory along boulevards. If a resident does have an ash tree removed and would like a replacement, the city will plant one of a variety of species.

"We've gotten dozens of calls, people wanting to get on the list," Shippee said. "Because it's voluntary, there's been very little negative reaction."

The emerald ash borer has not yet been detected in Blaine, but an infestation was found in the northwest corner of Shoreview, which borders the city's southeast corner.

"We suspect it is in Blaine. We just haven't found it," Shippee said.

Jessica Schaum, the environmental officer in Shoreview, said the city has removed trees with confirmed cases and is working on further prevention. "It's going to be a mixed or balanced approach of removing some and treating some, with an emphasis on planting for diversity in the future," Schaum said.

Susan Burks is forestry invasive species program coordinator at the Minnesota Department of Natural Resources. She said the DNR has found five infestations in four counties since the beetle was first seen in the state in St. Paul in 2009.

"It'll take a while before the public starts to see major changes in our canopy structure, because the cities are being pretty aggressive about getting those down," Burks said.

Gradual transformation

Shippee said the gradual removal allows for a transition of the streetscape. The city removes and replaces only three or four trees on a block at a time, then waits a few years to return.

When Dutch elm disease struck several decades ago, Shippee said whole neighborhoods were transformed overnight. "It looked like a battle zone," he said.

After that, a lot of elms were replaced with ash trees, which were cheap at the time. Now, the ash borer is a threat to those.

"Most serious insect and disease problems are host-specific," Shippee said. "If we go back and replace a monoculture with a monoculture, then we've learned nothing."

To avoid a repeat of this problem, Blaine is using from 10 to 15 varieties of trees as replacements. To some "consternation," property owners do not have a say in which kind of replacement tree they receive, Shippee said.

"Ninety percent will want an autumn blaze or some kind of maple," he said.

Shippee said the replacement trees cost about $100 each. Blaine has $35,000 to spend on replacement trees over the next two years -- $25,000 from a grant from the DNR and $10,000 from the city's matching portion.

Some cities, such as Shoreview, also are using insecticide injections to preserve some of their ash trees.

Shippee said that Blaine would consider treating high-quality ash trees in some high-visibility areas to prevent removal, but that treatment is not a cost-effective option for all trees.

"We have tens of thousands of trees. It just wouldn't be reasonable for a city to do."

If residents do not want their ash trees removed, the city provides them with information on treatment.

"Being voluntary keeps it positive," Shippee said, "because at some point, if boulevard trees actually start getting emerald ash borer, it's not going to be voluntary."

Bryna Godar is a Minneapolis freelance writer.