Maggie Koreth-Baker in The New York Times:
This past winter was the coldest Detroit had experienced in 36 years. Across the upper Midwest, cities shivered, and more than 90 percent of the surface area of the Great Lakes froze solid. It seemed like ideal weather to kill an unwanted insect. But it did little to stop the emerald ash borer, an invasive Asian beetle that is devastating ash trees from Minnesota to New York. “We didn’t find a single dead larva,” said Deborah G. McCullough, a professor of entomology and forestry at Michigan State, who led a study of ash trees in Lower Michigan over the winter. Even before the severe winter, Dr. McCullough and other scientists had come to the glum conclusion that they were going to lose the decade-long battle against the ash borer. Now they are assessing the cascade of consequences for Midwestern and Northeastern forests, both urban and wild. The effects will go far beyond what you see on a hike or how you feel about the loss of a tree on your property. They will ripple through forest ecosystems, affecting other plants, animals and water supplies.
Emerald ash borers do their damage as larvae, eating into the bark and burrowing deep into the trunk to insulate themselves against the cold. In the process, they cut off access to the nutrients and water that the tree needs to survive; it is like severing a human’s network of veins and arteries. After surviving the unusually cold winter, the beetles emerged in spring as adults. Now they are mating and laying eggs, leaving the next generation of larvae to tunnel through the trees’ internal organs. They can kill an ash tree in as little as two years.