On the Air: Who’s Cutting Down Our Urban Forests?


You may have noticed many beautifully formed lush street trees and park trees being cut down over the past few years. Most of these are ash trees that are suffering from an infestation of emerald ash borer. At EcoMyths we wondered: Why do the trees have to be cut down? Is there any other way to control the emerald ash borer? What can people do to help?

In honor of Arbor Day on April 26, these and other questions were probed on our latest EcoMyths Worldview segment.

Our expert guests were Peter Gordon, forester for the City of Lake Forest, Illinois; and David Horvath of the Care of Trees. Several communities in northern Illinois, including Lake Forest, as well as EcoMyths partners the Morton Arboretum and the Chicago Botanic Garden are campaigning urgently this year to raise awareness of the emerald ash borer (EAB). This is not an insignificant issue for Chicago—there are nearly 13 million ash trees in the region that could become diseased and need to be cut down. Naturally, we needed to know more.

Our conversation revealed some important points:

  • They’re newcomers: EAB was first spotted in Illinois in 2006 and originally found in the U.S. in 2002 in Michigan. The little creatures originated in Asia and are believed to have come over in wooden crates made from ash.
  • Warning signs: The little bugs are only about 1/2 inch long and are an iridescent green color. They’re hard to spot, so it’s easier to find infected trees by looking for:
    • Dieback of the topmost leaves on the tree
    • Large holes from woodpeckers trying to eat the EAB larvae
  • Cut ’em down! EAB infected ash trees need to be cut down quickly because they become brittle and can more easily fall down, causing safety concerns. In addition, removing dead trees helps control further infestation of other ash trees.
  • Whodunnit? It’s the larvae of the EAB that kills the trees. They create crisscrossing tunnels under the bark that prevent the tree from pulling water and nutrients in to sustain the tree.

What’s a Person to Do?

We also asked our guests how a person can help. Peter, as a city forester, is responsible for protecting healthy ash trees and for ensuring that infected trees are removed. As with other city foresters, he knows where most of the ash trees in his city are located—especially those lining the city’s streets and in its parks.

  1. Decide which ones to save: The ones that are most beautiful and important to the landscape can be inoculated from EAB if they are still healthy. You can help your city by reporting trees you see that show signs of EAB damage.
  2. Save healthy trees with pesticide injections: David, who works for a private tree company, helps homeowners save their most valuable ash trees. Certified arborists like him can help you decide which trees are worth the expense of saving based on the health and size of the tree. Pesticides can be injected into the tree to protect it systemically. If a tree cannot be saved, tree care companies will cut down and remove the tree. Injected pesticide stays simply within the tree and does not affect the surrounding area or other plants.
  3. Plant a variety of tree species: In addition to choosing which ash trees to inoculate and which to remove, both experts recommended replacement trees be of many different varieties. The more tree varieties in a local area, the more robust the tree population will be into the future because most of the trees are likely to be unaffected by diseases and pests that target a specific species like ash.

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—As part of our partnership with Worldview, this content may also appear on the Chicago Public Media EcoMyths series page.