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City to spend $2 million to treat 35,000 trees infected with emerald ash borer

Bark is scraped away from tree Chicago Botanic Gardens reveal an emerald ash borer larvae. | Tom Tiddens~Provided Photo

Bark is scraped away from a tree at the Chicago Botanic Gardens to reveal an emerald ash borer larvae. | Tom Tiddens~Provided Photo

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Updated: May 29, 2013 6:20AM

The Department of Streets and Sanitation announced a plan Wednesday to inoculate 35,000 parkway trees infected with the emerald ash borer this year at a cost of $2 million, with an expectation to treat the city’s remaining infected trees next year.

City foresters will inject an insecticide directly into the tree’s cambium layer, allowing it to spread via sap throughout the entire tree — a treatment the department spokesman called a safe and common solution for emerald ash borer infestation that will save the city millions in tree removal costs.

The emerald ash borer, an invasive beetle species known for its devastation of ash tree populations, needs around seven years to kill a tree — but the greater the infestation of the beetle, the faster the tree’s death. The first infected tree in Chicago was found in the 2600 block of South State Street in 2008.

That’s why the city is spending more than the $1.4 million a year the City Council Finance Committee recommended in a resolution passed in 2012, according to Streets and Sanitation spokesman Anne Sheahan.

“When we looked at the scope of the insect, we determined that we wanted to address as many [trees] as quickly as possible,” Sheahan said.

Of the estimated 85,000 trees infested with the bug on city property, Sheahan says 70,000 will be treated with the pesticide — half this year and the other half next year. The treated trees will be reassessed in three years, and those that respond well will be treated again while the most damaged will be removed.

Sheahan said the cost of inoculation is around $46 per tree — as compared to the $1,000 it could cost to remove the tree altogether.

The emerald ash borer program allowed Streets and Sanitation to hire and train 26 general laborers to apply the pesticide, which is expected to start in early May.

The pesticide, emamectin benzoate, is expected to kill 99 percent of the borers in a tree, though Sheahan said it is safe for the environment and people near the treated trees.

The treatment is also being used at the Chicago Botanic Garden in Glencoe, though supervisor of plant health Tom Tiddens said the public garden is being more judicious than the city in applying it.

Tiddens expects to let three-fourths of his infected ash trees die — though they will apply the product to around 100 trees this May.

“We don’t think this insect is going to go away,” Tiddens said. “Trees [given the product] will need to be treated for the rest of their lives.”

When asked why he bothers trying to fight the bugs, Tiddens invokes the purpose of the garden.

“We are a living museum of plants,” he said. “We want to preserve ash trees for the future.”

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