D3057: Assessment of establishment and spread of Laricobius species in the Great Smoky Mountains National Park

Since its introduction to the Great Smoky Mountains National Park in 2002, the hemlock woolly adelgid (HWA) (Adelges tsugae), native to Japan, has killed a large portion of native eastern hemlock (Tsuga canadensis) trees and threatens to kill even more. This loss of hemlock trees will cause a cascade of ecological consequences due to the hemlock’s classification as a cornerstone species. With the ability of HWA to kill hemlock trees within 4 years when unimpeded, this invasive insect pest has become a serious threat to hemlock trees not only Park-wide but across much of the eastern United States. This loss of hemlock is devastating to the ecological heritage of the Park and may also effect populations of organisms that rely on the forest dynamics of hemlocks. One of the tactics used to reduce the spread of HWA and mortality of hemlock trees is the release of several species of biological control agents, including Laricobius nigrinus (introduced from the Pacific Northwest) and L. osakensis (introduced from Japan). Both of these species have been released at numerous locations in the Park. The objective of this multi-year research project is to assess the establishment, species composition, and spread of both L. nigrinus and L. osakensis, as well as hybridization of L. nigrinus and the native L. rubidus, in the Park. These results will inform management decisions related to HWA and enhance survival of hemlocks in the Park. Results also will improve mitigation efforts against HWA in other infested areas in the eastern U.S.