This week, we are returning with our series covering the common tree diseases and insect pests in the Chicago area to take a closer look at an especially destructive pest; the emerald ash borer.  The emerald ash borer is one of the most feared tree pests because they can kill formerly healthy trees in just one to two years after infestation.  Once an ash tree is infested with the emerald ash borer, there is often little that can be done to save...