Emerald ash borer (EAB) arrived at the Allegheny National Forest in Pennsylvania in 2012 and has rapidly been killing ash trees across the forest. Northern Research Station scientists, in partnership with State and Private Forestry, the Allegheny National Forest, and other partners, have been working on conserving white ash genetic diversity across the Allegheny. Using population genetic approaches, scientists determined that to optimize conservation of genetic diversity, insecticide application efforts should focus on treating many sites with at least 10 trees per site rather than treating many trees within a single site. The results also highlight how valuable it is to select the correct sites for treatment, with certain sites holding more genetic diversity than others. Performing genetic analyses before insecticide treatment and using that information to select sites with complementary genes can result in nearly a 30 percent cost savings. The results of this research will help forest managers plan their response to EAB and other forest pests and pathogens throughout the region.