Exotic animals and plants are crisscrossing the globe as never before. Many of these unwelcome species have found their way to the Chicago area and are wreaking havoc on our local ecosystem.

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NAME: Emerald ash borer (Agrilus planipennis)
DATE INTRODUCED: 2002; discovered in Illinois in 2006
HOW IT GOT HERE: Arrived in imported cargo

The emerald ash borer arrived last year in Kane County and spread as far as several North Shore towns, setting off alarms of an arboreal catastrophe. These tiny green beetles had already killed an estimated 20 million ash trees in Michigan, Indiana, and Ohio, making it “a much greater threat than the Asian long-horn,” says Summers. The insect feeds only on ash trees—which make up roughly 20 percent of the trees in the Chicago area. Adult borers feast on ash foliage, causing little damage. But the larvae feed on inner bark, cutting off the flow of nutrients and water to the trees, eventually killing them. 

THE FIGHT: The state’s department of agriculture set up ash borer quarantines in several northeastern Illinois counties to stop the movement of infected firewood, logs, and nursery trees. Entomologists are also considering releasing the borer’s native nemesis: a stingless wasp that eats the beetle’s eggs and larvae.