You are here

Harvard Forest >

Harvard Forest REU Symposium Abstract 2005

  • Title: Landscape survey of hemlock woolly adelgid and elongate hemlock scale abundance in hemlock forests of southern New England
  • Author: Alexandra G Lodge (Kenyon College)
  • Abstract:

    The hemlock woolly adelgid (Adelges tsugae) (HWA) and elongate hemlock scale (Fiorinia externa) (EHS) are invasive insects that feed on and cause decline and mortality of eastern hemlock trees (Tsuga canadensis). In this study I resurveyed 78 hemlock stands in central Connecticut and 63 stands in central Massachusetts that were previously sampled. At each site I randomly sampled two branches on each of 50 trees for HWA and EHS density, rated on a scale of 0-3 (0=none; 1=1-10 organisms/m branch; 2=11-100/m branch; 3=100+/m branch). Overall stand canopy loss was also assessed on a scale of 1-4 (1=0-25% loss; 2=26-50% loss; 3=51-75% loss; 4=76-100% loss). Canopy loss increased with increasing HWA density, with the most damaged stands located in southern CT and undamaged stands in northern MA. HWA density decreased with increasing latitude, possibly due to climatic limitations. EHS decreased with increasing longitude potentially indicating the front wave of the northeasterly expansion of the range of EHS. HWA density has decreased at almost all sites since the previous samplings, but the total number of infested sites has increased. EHS distribution and density have increased dramatically since the previous sampling – in 1997-1998, 22 of 78 sites in CT were infested with EHS, but EHS was present at all sites sampled in CT in 2005. These sites should be resurveyed in the future to monitor changing HWA densities and their affect on canopy loss and to further examine trends of the northern spread of HWA and EHS.

  • Research Category: