Western Springs Plans Dual Removal/Treatment EAB Strategy

With $40,000 in the 2012 budget devoted to chemically fighting emerald ash borer—an invasive species of bug deadly to ash trees that —the Village plans to pursue a 10-year strategy combining the treating and removing of parkway ashes.

Using a scale from one to six, in which one denotes a perfectly healthy tree and six a dead one, a forester has canvassed the Village’s 1300 roadside ash trees and determined those most likely to require removal this year. That includes seven “five” trees and several dozen “fours.” (A PDF map can be seen to the right.)

All seven of the Village’s “five-rated” (nearly dead) ash trees are slated to be removed this spring, along with any others that ail past a certain threshold. No healthy ash trees will be removed—just as under ordinary circumstances, only dead and dying trees will be culled.

The core objective of the dual treatment-and-removal plan is to avoid any scenario in which large number of trees in the same location must be removed at the same time, effectively denuding a roadway, explained Village Municipal Services Director Matt Supert.

“We don’t want to get in a situation where we’re tearing all these trees down,” Supert said. “There’s going to be some removal of the fours, to minimize the visual impact… We’ll kind of begin to phase out the ash trees over the next five, seven, ten years.”

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Bids for a treatment contract went out at the end of last week. Treatment would begin in June, and is required to be via direct injection into a tree trunk, instead of by spraying or soil-drenching, to avoid any undesirable side effects to the surrounding environment

Although final numbers will depend on those bids, Municipal Services expects to be able to treat about 300 ash trees in 2012 (most treatments last between one and two years.) Southeast Field Park, with the highest concentration of “three-” and “four-” rated ash trees, will likely be a center for 2012 treatment efforts, with additional trees selected Village-wide where necessary to preserve a roadside canopy.

“We’ll go as far as the budget allows us,” said Supert. “It’s our first foray into it, so I’m not sure where things will play out the next few years… The question is really over the next five years, how are we going to see the decline play out?”

Replacement trees, a choice of about a half-dozen types, paid for from Village coffers, are ordered from the Morton Arboretum. As Arboretum representative Sharon Yiesla explained, emerald ash borer, which originated in Asia and is named for its bright-green hue, kills ash trees when the beetle’s larvae tunnel into a tree’s tissues and cut off its water supply.

“This has turned into a serious test,” Yiesla said of Chicagoland’s dealing with EAB. “We have a lot wood-boring insects that just go to stressed or unhealthy trees, but the emerald ash borer will go to healthy trees, so all of our ashes are at risk.”

EAB doesn’t only attack parkway trees, of course. Residents with an ash tree on their private property may choose for themselves whether to treat or not. Most treatments have to be administered by a trained arborist. (Treatments are more effective before the beetle strikes, or in the earliest stages.) The only Village mandate is that, for safety reasons, dead trees do have to be removed from private yards.

“If residents want us to come out and take a look at it—let’s say they have an ash tree in their backyard and they’re just not sure—they can call the Village and have us come take a look at it,” Supert offered.

A complete brochure of information about EAB in the Village is scheduled to be mailed to residents later this week or early next.

While EAB poses a challenge to the Village, it is not wholly a unique challenge. Somewhat ironically, many of the endangered ash trees were planted as replacements for elm trees wiped out by Dutch elm disease in the 1970s. The experience of handling Dutch elm disease has provided a sketchy template for handling a threat to an expanse of Village trees.

Even today, Village staff still occasionally have to remove an elm tree stricken by Dutch elm, meaning that a few hardy ashes might hang on that long as well.

“I would not be surprised if 15, 20 years from now there are still ash trees in town, and in 15 or 20 years maybe we’ll still have ash trees getting EAB that’ll need to be removed,” Supert said. “We’ll take the trees as they come.”