What is this bug coming for the Ash Trees?

Originally from Asia, the emerald ash borer (EAB) was first discovered in the Detroit area in 2002.
The emerald ash borer primarily lives in the midwestern and eastern United States and parts of Canada, but is spreading fast. Nashville is expected to lose nearly 10% of tree canopy to EAB over the next several years.
Symptoms of EAB include thinning or dying of ash tree crowns, suckers at the base of the tree, splitting bark, tunneling under the bark, D-shaped exit holes and woodpecker activity.
Treatment options exist ranging from $50 to $250 per tree based on the Ash trees size and can be applied in peak growing season of May through August.
Plentiful information exists to help home owners understand the risks and costs with treatment and removal: http://www.emeraldashborer.info