The nearly 90-foot-tall green ash tree growing on a central Illinois property is the largest of its kind in the state, and that makes it worth protecting, a forestry expert says.
An arborist on Monday treated the tree, located in Clinton, to protect it from the emerald ash borer, the invasive metallic green beetle that's killed millions of trees across the Midwest.
University of Illinois forestry specialist Jay Hayek says green ash is one of the four species of ash that are native to Illinois, and the ash borer is a threat to them all. Hayek also keeps the Illinois Big Tree Register, the official list of the largest specimen of each type of tree found in the state.
"The research that we have now, they're all susceptible," he said. "I would say that green ash is very susceptible."
The ash borer is native to Asia and wasn't found in North America until 2002, according to the Illinois Department of Agriculture. The ash borer's larvae kill trees by feeding on the inner bark. Ash borers have so far been found in at least 29 Illinois counties, mainly in northern and central Illinois.
A Massachusetts company, Arborjet, treated the tree for free after the family that owns the property contacted state officials looking for help, according to Jim Prendergast, who handles public relations for Arborjet.
"The chemistry is injected into the tree in sort of an IV method," Prendergast said.
Such treatments can be effective, but also expensive - $100 or more every two or three years per tree, depending on the type of treatment, said Warren Goetsch, the state Department of Agriculture's bureau chief of environmental programs
"You're going to have to treat, in essence forever, or as long as you want that tree to remain," Goetsch said. "But there are some instances, and I think this is an excellent example of one where you do have a unique tree."
The city of Chicago is spending $46 a tree in a program intended to treat 35,000 ash trees this year at a cost of about $1.6 million. Mayor Rahm Emanuel has said it would be far more expensive to cut down and replace trees at about $1,000 a tree.
Some reports put the green ash in Clinton's age at 150 years, but Hayek said it's almost impossible to know for sure. Green ash trees grow relatively fast, so it could be as young as 80 or 90 years.
The tree has been considered the biggest of its kind in the state since 1988. Hayek visited it himself just about a month to get some updated measurements, he said.
But it could soon have a challenger.
"Actually I received a phone call this morning from a gentleman in Decatur who says his tree is larger," Hayek said.
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