There are an estimated 8 billion ash (Fraxinus) trees in North America. These species are of great value in managed landscapes (street and park trees and windbreaks), for their wood products (lumber, tool handles, baseball bats, baskets, etc.), and in natural forest ecosystems. An introduced pest from northeastern Asia, the Emerald Ash Borer (EAB), Agrilus planipennis Fairmaire, is killing all native Fraxinus in Michigan, Indiana, and Ohio, and now spreading into surrounding states and Canadian provinces. So far, tens of millions of trees have died at great economic and ecological cost. Based on ongoing evaluations, no native North American populations are yet known to be resistant to EAB. The loss of these ash species has cultural, ecological, and economic implications that warrant preserving the genetic resources before too much is lost to the insect.
Trees, as do all plants, must be adapted to their environment to thrive. Over the centuries, natural ash populations have adapted to their environments, and preserving a significant number of these populations is required for successful reintroduction of ash once adequate control measures for EAB are developed or ash trees resistant to the insect are developed. Breeding resistant ash trees for reintroduction will ultimately require an array of adapted parental populations. Given the projected degree of EAB destruction to native stands, only adequate ex situ germplasm collections protected from EAB will be able to provide this needed material. When seed quantities and quality are sufficient, ash accessions curated in the NPGS active collection at the North Central Regional Plant Introduction Station in Ames, Iowa are freely available to support the scientific research and educational efforts that will be needed to overcome EAB.
In northeastern Asia, EAB has coevolved with a different set of Fraxinus species than are native to North America. In order to give access to potential sources of EAB tolerance or resistance to researchers, it is also important to assemble, conserve, and evaluate Asian ash germplasm.