What are lingering ash?

Lingering ash are those mature, native, untreated ash trees that persist in healthy condition significantly after the vast majority of mature, native, untreated ash in the same area have been killed by EAB. Research led by the USDA U.S. Forest Service has shown that selective breeding of ash trees derived from scion (twig samples) taken from lingering ash can yield highly EAB-resistant trees within two generations, offering tremendous hope for ash conservation. A compelling presentation on this project can be seen at https://youtu.be/gz5vKBHDqUY?si=WCkfmV2acfxBxB1A.