Emerald ash borer, an invasive insect that attacks ash trees, is the most destructive forest insect in North America. It has been found in more than twenty Midwestern and Eastern states and has killed tens of millions of ash trees since its initial detection in 2002. It is readily transported in hardwood firewood, ash wood products, and ash nursery stock. Early detection is critical to success and cost of management programs. Learn the signs and symptoms associated with emerald ash borer infestation in ash.