reach levels lethal to healthy trees. In China, it infests native Fraxinus chinensis, F. mandshurica, and F. rhynchophylla; in Japan it also infests F. japonica and F. lanuginosa. Emerald ash borer primarily infest and can cause significant damage to ash species including green ash (F. pennsylvanica), black ash (F. nigra), white ash (F. americana), and blue ash (F. quadrangulata) in North America. In Europe, F. excelsior is the main ash species colonized, which is moderately resistant to emerald ash borer infestation. Ash susceptibility can vary depending on the attractiveness of chemical volatiles to adults, or the ability of larvae to detoxify phenolic compounds. Emerald ash borer has also been found infesting white fringe tree in North America, which is a non-ash host, but it is unclear whether the trees were healthy when first infested, or were already in decline because of drought. Another non-ash host has also been discovered, Olea europaea, albeit in a lab setting. Adults prefer to lay eggs on open grown or stressed ash but readily lay eggs on healthy trees amongst other tree species. Ashes that grow in pure stands, whether naturally occurring or in landscaping, are more prone to attack than isolated trees or ones located in mixed forest stands. Ashes used in landscaping also tend to be subjected to higher amounts of environmental stresses including compacted soil, lack of moisture, heating effects from urban islands, road salt, and pollution, which may also reduce their resistance to the borer. Furthermore, most ashes used in landscaping were produced from a handful of cultivars, resulting in low genetic diversity. Young trees with bark between to are preferred. Both males and females use leaf volatiles and sesquiterpenes in the bark to locate hosts. Damage occurs in infested trees by larval feeding. The serpentine feeding galleries of the larvae disrupt the flow of nutrients and water, effectively girdling, thus killing the tree, as it is no longer able to transport sufficient water and nutrients to the leaves to survive. Girdled ashes will often attempt to regenerate through stump sprouting, and there is evidence that stressed trees may also generate higher than normal seed crops as an emergency measure. Invasiveness Outside its native range, emerald ash borer is an invasive species that is highly destructive to ash trees in its introduced range. Before emerald ash borer was found in North America, very little was known about the insect in its