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The Emerald Apocalypse
How Milwaukee got off its ash and did something about the worst threat to trees since Dutch elm disease.

When the emerald ash borer was finally spotted in Milwaukee this summer, no one in city government was surprised. Its tree guru, Forestry Services Manager David Sivyer, had been awaiting the discovery for years. Like any number of officials in similar positions in similar cities, he knew the invasive Asian beetle, which resembles a metallic-green grain of rice, was slowly but surely eviscerating the country’s ash trees. It was only a matter of time before Milwaukee’s ticket got punched.

Yet as Mayor Tom Barrett inspected an infected tree’s split bark and D-shaped holes (telltale borer signs) at a July press conference, Sivyer glanced across the road to 80th Street, where rows of city-managed ashes stood strong and healthy. Unlike the damaged tree, which was privately owned, these had been injected with a borer-battling serum by city workers. “I told the mayor if he hadn’t taken that step,” Sivyer says, “the press conference could have been over on 80th Street.”

The first borer spotted in Wisconsin was found in 2008 in the village of Newburg, a small town overlapping the line between Ozaukee and Washington counties. Experts say that by the time a beetle is found in a community, the insects have already been there for four or even five years. Expecting an onslaught on tiny bug feet, Sivyer and the city got ready. As a result, few cities are more prepared than this one to weather a brush with the borer.

How Milwaukee found and injected (almost) all of its ashes
This emerald pest threatens to inflict damage on the scale of Dutch elm disease, which all but wiped out America’s once-splendorous canopy of elm trees in the 20th century. No suburb has been as proactive as Milwaukee, including Franklin, where officials are treating trees using a soil-based method that Sivyer says isn’t as effective as the injection strategy.

In Greenfield, City Forester Dennis Fermenich has been cutting down weakened ash trees 
that are especially vulnerable to infestation and stopping private developers from planting new ones. Next to healthy ashes, he’s planting other species of trees, so that if the ash goes down, the street won’t be stripped.

When citizens of Shorewood caught wind of Milwaukee’s inoculation program, a public outcry forced the North Shore community to inject its trees as well, though in a more “seat of the pants” fashion, according to Ian Brown, a technical services manager for Milwaukee’s Department of Public Works. 

How the suburbs are responding to the borer’s grave threat
Even before the ash borer was detected in Wisconsin, Sivyer and his team were preparing for its arrival. Their first step was finding the bug’s favorite meal. “If we had any hope of managing this proactively,” he says, “we needed to know where the ash was.”

The forestry department deployed a “hyperspectral” camera developed by the U.S. Department of Defense for finding tanks in jungles and marijuana bushes in corn fields. Flying over the city, they succeeded where the U.S. Forest Service had failed and mapped all 587,000 of Milwaukee’s ash trees, including 33,000 on city property.

“I had some skepticism, but then we started seeing stuff like this,” Sivyer says, pointing to a brightly colored map with ash trees highlighted in red. The difference between Milwaukee’s data collection and earlier efforts, he says, was the range in wavelengths measured. The city parsed the spectrum more precisely than federal officials had in other cities, allowing it to sort ash trees from other species. Workers injected 27,000 of the ashes on city land and disregarded another 6,000 deemed unfit due to small size or poor health.

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