Chicago to treat parkway ash trees against beetle
Tuesday, April 23, 2013
by Rachael Levy
Ash trees within Chicago's parks and the Cook County forest preserves will continue to be cut down and replaced as a result of the emerald ash borer infestation, but those along the city's parkways will be treated starting around May 6, officials said.
The emerald ash borer, a tiny beetle laying waste to the region's ash trees, arrived in the U.S. from Asia about a decade ago and was first spotted in Chicago in 2008, according to Mike Brown, assistant general superintendent at the Bureau of Forestry, which falls under the Department of Streets and Sanitation.
The bureau stopped planting ash trees in 2003, Brown said. Now it will try to save many of the surviving trees lining the city's parkways.
"The ash trees make up a little less than one-fifth of our street tree population and so we feel it's worth trying to save them," Brown said, explaining that the bureau tried a limited test run in 2009.
Out of the 85,000 ash trees lining Chicago's streets, the Bureau of Forestry will attempt to save 70,000 using an insecticide called Tree-age, or emamectin benzoate, which is injected directly into the tree, Brown said.
"The other 15,000 I think we're going to lose," he said. "They're too far gone."
The treatment will cost $46 per tree, including labor, Brown said. The treatment will be repeated every three years at the same cost, he said.
Removing and replacing one of the parkway ash trees, which average 16 inches in diameter, would cost about $1,000, said Anne Sheahan, public affairs director at the Department of Streets and Sanitation.
The city has budgeted $2 million this year to treat the parkway ash trees, up from $110,000 last year, Sheahan said.
"It's a huge investment the mayor is making in forestry and the emerald ash borer alone," she said.
The Bureau of Forestry will start by focusing on areas like the 3rd Ward, where the insect was first found five years ago, Brown said.
"We're going to start in the areas that we know are infested and haven't been treated," he said, adding that 26 laborers have been hired to work on the project.
The treatment process will continue until the end of September or early October, at which point the bureau hopes to have treated about half, or 35,000, of its trees. It will treat the remaining trees the next year, Brown said.
Widespread injections aren't practical in the Forest Preserve District of Cook County because of its large number of ash trees, according to John McCabe, deputy director of the preserve's Department of Resource Management. The preserve is home to about 10 million trees, 15 to 20 percent of which McCabe estimates are ashes.
While he acknowledged that treatments may have improved since the insect was first spotted in Chicago in 2008, McCabe said he doubts their effectiveness.
"We're the largest landowner in northeast Illinois. ... We'd be paying to treat trees that we'd be cutting down anyway," he said. "And with the number of trees we have, and the resources we have, we felt like we needed to remove the trees."
Since 2008, the preserve has been removing ash trees and replacing them with a variety of species only in areas frequented by the public, McCabe said. It costs $400 to $800 to replace one ash tree at the preserve, depending on factors like the species of tree and maintenance costs, he said.
A similar philosophy is playing out in the city's parks. The Park District expects to replace 20,000 to 25,000 ash trees, about 10 percent of the trees in Chicago parks, according to a spokeswoman. In the last six years the Park District has been replacing the ashes with shade trees of other species, such as maple and hickory, she said.
The cost to install, maintain and warranty new shade trees in Chicago parks averages $750 per tree, while treating them with Tree-age would cost $135 every two years, including labor costs from an outside contractor, the spokeswoman said.
After 30 years, "we'll have spent over $2,000 on a now-overmature ash tree which is likely in decline (if the tree has survived at all; ash are rarely long-lived species)," according to a Chicago Park District statement. "We will also have lost up to 30 years of growth of two to three new trees (such as oaks, maples, and other long-lived species) that (we) could have planted with the funds spent on inoculation.
"The city's Forestry Division's decision to treat instead of remove the ash trees has a lot to do with the fact that if they removed all ash trees from the parkways, it would result in streets exposed and bare. Whereas, removal of the ash trees in city parks would not leave an exposed and bare landscape since there will be many trees (of other species) left behind," the statement continued.
Not everyone is happy with replacing the ash trees in Chicago's parks.
"I think any decision to just let them die is morally wrong, environmentally unsound and economically stupid," said John Friedmann of the Save the Ash Tree Coalition in an email.
The coalition will hold a meeting for North Side homeowners with Ald. Richard Mell, 33rd, and four other aldermen at 7 p.m. Wednesday at the Lane Tech College Prep auditorium, 2501 W. Addison St. The meeting will lay out Chicago's plan to combat the infestation and steps that homeowners can take to save their ash trees.