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Globalization and Invasive Species Take Toll on America's Trees

Tom Pelton


A white ash tree stands beside my front porch in Baltimore -- its trunk nearly as thick as I am tall, and its branches stretching at least three times the height of my three-story house, shading one side of my roof to the other.

It’s about 200 years old, and it started growing back when this section of the city was still farmland beside a stream, decades before the Civil War.

From one of its massive branches, I hung a rope swing that my daughters flew on through the air in their white first communion dresses many springs ago, and that all my neighborhood’s children adopted as their swing.

But recently my old friend hasn’t been looking himself.   The tips of several of its high branches never grew leaves this summer.  So I called in a tree doctor: Matt Mitchelltree of North Hill Tree Experts.

“Well the tree definitely has emerald ash borer, which is an invasive insect we’ve been dealing with over the last five six years," Mitchelltree said. "It does a lot of internal damage to the plant, which causes die backs in the tips and eventual death of the tree.”


It was a diagnosis I’d been dreading to hear since the emerald ash borer – a shiny green beetle from Asia that loves ash trees and has no natural predators in the U.S.  – in the 1990s hitchhiked over from China to the suburbs of Detroit, likely in the wood of a packing crate.

Despite efforts at quarantine and pre-emptively cutting down tens of thousands of ash trees to stop their movement, the beetles spread across the Eastern US and Maryland.  Around 2004 in Prince George’s County, the Maryland Department of Agriculture tried an aggressive strategy to halt their spread– mowing down all ash trees within a mile and a half radius of infected trees.

Here’s Heather Disque, an entomologist with the state agency.

“The beetles flies much better than we had originally anticipated, and it flew past our quarantine efforts," Disque said. "And since then we have quarantined the entire state for emerald ash borer.”

As many as 6 million ash trees worth more than $200 million could be lost in the Baltimore area alone.

For me, the personal price tag will be steep. The would be about $10,000 to cut down my infected ash tree – or $600 per year – in perpetuity – to treat it with pesticides.

As an alternative to pesticides, Maryland and other states are trying they call “biological pest controls.” State biologists are releasing tens of thousands of Asian parasitic wasps that lay their larvae in and kill the emerald ash borer, as they do back in their native China.

Carrie Brown-Lima, Director of the New York Invasive Species Research Institute, said that newly introduced control species like the Asian parasitic wasps have been carefully screened.

“Now a days, with the amount of invasive species we have, and how widespread they are, biological controls are turning out to be one of our only long-term sustainable solutions to our invasive species problems," Brown-Lima said.

I’m skeptical that this will work -- or that these tiny wasps will save my giant friend.  But I suppose the only other solution is turning back the hands of time, before Europeans arrived on this continent as an invasive species, to wipe out Native Americans and start the process of globalization that now returns to haunt us, like an infected tree.



Tom Pelton, a national award-winning environmental journalist, has hosted "The Environment in Focus" since 2007. He also works as director of communications for the Environmental Integrity Project, a non-profit organization dedicated to holding polluters and governments accountable to protect public health. From 1997 until 2008, he was a journalist for The Baltimore Sun, where he was twice named one of the best environmental reporters in America by the Society of Environmental Journalists.