By Michelle Werts

Every day, our forests and trees are under assault: from droughts, tornadoes and hurricanes to fires and climate change. One particular brand of threat, though, is often sneaky, small and numbers in the thousands: insects.

Emerald ash borer
Emerald ash borer. Credit: David Cappaert, Michigan State University/

Trees and insects can often have a symbiotic relationship, with the insect providing pollination and other services to the trees, while the trees provide the insects with food and protection. Sometimes, though, those insects become unwanted houseguests and deadly serial killers.

Last week, the Chicago suburbs Batavia and Deerfield each announced that they would be removing hundreds of ash trees due to damage and death caused by the emerald ash borer (EAB). With its iridescent green body, EAB may look pretty, but it leaves nothing beautiful in its wake.

First found in the U.S. in Detroit, Michigan, in 2002 — when it likely arrived via wood in cargo bays on ships from Russia, China, Japan or Korea — this non-native pest has been destroying ash canopies throughout the Midwest and Canada and continues to spread. And they’re likely to be on the move again soon.

Injecting an ash tree to protect against EAB
Injecting an ash tree to protect against EAB — mauget capsules are used to inject nutrients or pesticides into cambium layer for uptake by the tree. Credit: David Cappaert, Michigan State University/

Like many insects, EAB larvae spend the winter growing, protected in their host tree. Come spring, they emerge and find new ash trees on which to feed and ultimately destroy. With this year’s early spring, forest officials are already preparing for the re-emergence of this killer. Last week, a handful of states, including Georgia, Virginia, Wisconsin and Minnesota, announced plans to hang thousands of traps on their trees in hopes of staving off the spread of EAB to their forests. The traps are designed to attract EAB through their color and scent, which mimics that of a stressed ash tree. Foresters hope that these traps will be able to capture the elusive insect and provide early warnings for areas at risk, allowing officials to possibly invest in expensive injections and other chemical treatments to the trees to prevent infection.

The best treatment option currently available, though, is removal of the infested trees in hopes of preventing the spread of EAB to the healthy ones. As a result, some communities are at risk of losing a large percentage of their canopy — Whitefish Bay, Wisconsin’s canopy is almost 50 percent ash — which will diminish the overall well-being of the community’s ecosystem. As a result, the USDA Forest Service is actively issuing grants to communities to replace trees in affected areas, and our Global ReLeaf work to restore forest areas — both urban and rural — in the Midwest is more important than ever.

And, unfortunately, EAB isn’t the only threat our forests are facing. So this Earth Month, head over to our Forest Threats page to learn about more of the issues facing America’s forests and how you can help.