Ash borer may claim 15 percent of Highland Park’s parkway trees
City forester Joe O'Neill points out the tunneling pattern of Emerald Ash Borer larva on an infested tree on north Sheridan Road in Highland Park. I David Banks~for Sun-Times Media
Updated: February 25, 2013 11:23AM
HIGHLAND PARK — City Forester Joe O’Neill knew what he’d find Monday when he peeled off a patch of bark on an ash tree on the 2600 block of Sheridan Road.
The telltale signs of Emerald Ash Borer infestation could be seen in the checkerboard markings left by woodpeckers in search of the borer’s larva beneath the surface.
Sure enough, the exposed trunk showed the tunneling pattern indicative of the larva.
“The larva is there and the woodpeckers are hungry,” explained O’Neill.
The forester estimated the ash borer had been present for several years. However, the infestation was difficult to detect until woodpeckers began poking away at the bark.
“It is very difficult to identify,” he said. “You can see the woodpecker holes, but you don’t see the D-shaped exit holes created by the borer. Right now, some ash trees in Highland Park show it badly and others do not.”
In this case, the two trees on either side of the infested ash are Norway maples and therefore of no interest to the Emerald Ash Borer. The Emerald Ash Borer, however, can fly for up to 1.5 miles, so ash trees in a much larger area are at risk.
The City of Highland Park stopped planting ash trees in 2003 after the bug was first confirmed in Michigan in 2002. It’s believed to have arrived in the United States from China via shipping crates.
Highland Park’s first confirmed case was found in 2011 near Sheridan Road and Oakmont at the southern end of the city. The spread has been accelerated by drought conditions for the past two years.
The city has about 4,200 ash trees on its right-of-way, representing about 15 percent of the street tree population. About 20 percent of trees on private property also are ash.
While healthy ash trees will remain until they show signs of stress, the city’s management plan calls for removing all ash street trees over the next six years and replacing them with another variety. Early efforts will focus on large trees already affected due to the risk to public safety. Parkway trees removed due to ash border will be replaced at no cost to the resident. The goal is to replant trees within 18 months of removal.
Highland Park’s management plan does not call for using chemical treatment due to the high recurring cost of injections and community concerns about pesticides. Treatment may be considered in the future as economics and techniques evolve.
“Once Emerald Ash Borer is established in a community, it is never going to go away,” O’Neill said. “Treatment would be a cost the city would incur for the rest of the life of the tree, though in the short term it would be less expensive.”
A single injection for a 14-inch diameter tree is about $84, compared to $112 for removal of the tree and its stump.
Private property owners have the option of treating their affected ash trees, and should contact a certified arborist to discuss their options. The city may require a homeowner to remove an affected ash tree — or any tree — that poses a risk to the public.