Like a dreadful disease, the emerald ash borer is insidious, inevitable, and deadly.

Insidious because the insects – or, more specifically, their hungry larvae – are already chewing up ash trees from the inside long before you know they’re around.

Inevitable because, since they were first found in the U.S. 11 years ago, emerald ash borers have steadily swept across the country.

Deadly because, with their exponential reproduction and voraciousness, the insects are wreaking havoc on Midwestern ash trees: An estimated 50 million trees are dead or dying because of the bugs, the Wisconsin Department of Natural Resources estimates.

The emerald ash borer may reach Eau Claire this year or maybe next, but this much is certain: It will strike eventually. “To be honest with you, the insect may already be here,” explains Todd Chwala, the city’s superintendent of parks, forestry, and cemeteries. “However, the population of the insect hasn’t reached a point where it’s completely evident.”

Experts estimate that the bugs may be established in an area for four to five years before they are discovered. So by the time someone spots them here, it will already be too late for the estimated 38,000 ash trees in Eau Claire. That’s why, Chwala says, the city is taking proactive steps to deal with the inescapable plague.

“To be honest with you, the insect may already be here. However, the population of the insect hasn’t reached a point where it’s completely evident.” – Todd Chwala, Eau Claire superintendent of parks, forestry, and cemeteries, on the emerald
ash borer

The ash borer, a native of Asia, has spread to 18 states and 15 Wisconsin counties. Last summer, it was found in Perrot State Park in Trempealeau County, about 60 miles south of Eau Claire. Adult ash borers are metallic green and about one-third of an inch long – or about the size of a cooked grain of rice. Adults emerge from D-shaped holes in ash trees between late May and mid-July, and only live three to six weeks, but in that time females each lay 60 to 90 eggs in the crevices of ash tree bark. During their larval stage, the insects live under the bark and eat their way through the trees, eventually killing them.

As of 2006, ashes made up 30 percent of the trees on public property in Eau Claire. By the time the insect invader arrives, Chwala wants that figure to be 20 percent, which means cutting down thousands of trees. Culling the ash trees now will keep the city from having to remove thousands of dead or dying trees in a few years when the work will be more costly and overwhelming. Doing it now also will give replacement trees a head start so they may be big enough to provide shade and other benefits by the time the ash apocalypse occurs.

Some neighborhoods will be hit hard: Ashes make up a whopping 41 percent of the trees in the Golf Road/Fairfax Street neighborhood and 38 percent in Putnam Heights. “Even if the emerald ash borer wasn’t threatening our community, it would be in our interest to thin and cull a population that is overrepresented,”Chwala says. The city is replacing ashes with a wide variety of trees, including swamp white oaks, disease-resistant elms, magnolias, hackberries, fruitless horse chestnuts, ginkgoes, honey locusts, Kentucky coffee trees, and London planes. Two years ago, the city created an ash borer readiness plan. Since then, about 1,150 ash trees have been cut down on boulevards and other public property, bringing their share down to 26 percent of the city’s public trees. Many of these trees have been removed as part of regular street projects. Others have been cut because they are under power lines or atop city infrastructure. The city budgets $50,000 annually for shade-tree replacement, and the City Council has committed to increasing that as needed, Chwala says. This spring alone, the city will plant about 485 trees in parks and boulevards – none of them ash trees, of course.

Chwala acknowledges that cutting down so many trees is bittersweet. However, he’s grateful the ongoing plague has raised awareness about the need for a healthy canopy of trees in cities, where they control water runoff, clean the air, provide shade, and sequester carbon.

“For me to have a sense of dread coming to work … I can’t do that,” Chwala says. “I have to see the silver lining, and I intend to.”

WOOD YOU BE CAREFUL

One way to slow the spread of emerald ash borers is to be careful moving firewood. The Department of Natural Resources prohibits bringing firewood onto DNR land if it comes from more than 25 miles away or from outside the state. State and federal quarantines also prohibit moving firewood out of emerald ash borer quarantine areas. To learn more, go to emeraldashborer.wi.gov.