About Emerald Ash Borer . The emerald ash borer (EAB) is an invasive insect that has killed tens of millions of ash trees since it was first discovered in 2002. EAB kills all ash tree species and is considered to be one of the most destructive tree pests ever seen in North America. The larvae of the insect feed on live tree tissue, damaging the Learn more about ash lumber. How the Emerald Ash Borer is Killing the Ash Trees. Emerald Ash Borers are likely to kill 99 percent of the U.S. Ash wood trees, says the U.S. Forest Service. This exotic insect girdles and kills the tree. The killer beetle has made a home in 26 states, two Canadian Providences and is continuing to spread. The emerald ash borer (Agrilus planipennis) is an invasive wood-boring beetle: the adult beetle is ⅜” – ” long, has a flattened back and dark metallic green wings. The Asian beetle infests and kills native North American ash species (Fraxinus sp.), including green, white, black and blue ash.