Assessing relationships between tree diameter and long-term persistence of imidacloprid and olefin to optimize imidacloprid treatments on eastern hemlock

摘要

Hemlock woolly adelgid (HWA), Adelges tsugae (Annand), has caused widespread eastern hemlock mortality in the eastern U.S. HWA was first documented in Great Smoky Mountains National Park (GRSM) in 2002. Once documented, GRSM implemented an aggressive integrated pest management (IPM) program. As a part of this IPM strategy, systemic imidacloprid treatments have been widely used to preserve the Park's hemlock resources. A retrospective study was conducted in cooperation with GRSM to examine the long-term effectiveness of imidacloprid treatments on different size hemlock trees. Of particular interest is olefin, a metabolite of imidacloprid, which is greater than 15 times more toxic to HWA than imidacloprid. The concentrations of imidacloprid and olefin were assessed in hemlock branchlets four to seven years post-imidacloprid treatment. Samples were collected from three strata of the canopy from each of four size classes (30, 45, 61, and 76 cm DBH).