Emerald ash borer (EAB), Agrilus planipennis Fairmaire, is an exotic beetle that was discovered in the U.S. in 2002. The adult beetles nibble on ash foliage but cause little damage. The larvae feed on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients.
They probably arrived here on wood packing material carried in cargo ships or airplanes originating in its native Asia. Since its discovery, EAB has killed hundreds of millions of ash trees in North America.