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Harvard Forest REU Symposium Abstract 2006

  • Title: The effectiveness of chemically treating Eastern Hemlock trees to fight Hemlock Woolly Adelgid Infestations
  • Author: ()
  • Abstract:

    Hemlock Woolly Adelgid (HWA) is an invasive pest from Japan that threatens many populations of Eastern Hemlock. As HWA infestation has become widespread and more severe, many efforts have been made to help stop the devastation and possible elimination of Eastern Hemlock trees in infested areas. Although there have been several attempts at biological control, chemicals are currently the most effective form of HWA management. These chemicals are either applied topically to infested foliage or systemically to the soil and roots or injected directly into the trunk. For this study, three sites in Massachusetts and one in Connecticut that have been treated using different methods were surveyed for treatment impact on HWA populations. At each site, both treated and nearby untreated trees were assessed for overall health and HWA infestation levels. Measures of tree health included vigor, transparency, density, and live crown ratio. Eight branch tips on each tree were examined for presence and degree of infestation of HWA and amount of new growth by the tree. At all four sites, chemical treatments were successful in keeping HWA infestations lower than on surrounding, untreated trees. The effects of treatments on overall tree health were not uniform. In sites with heavy infestations, treated trees exhibit much better health than their untreated counterparts. In these cases, treated trees tended to have much better vigor, transparency and new growth scores. In areas with more mild infestations, there is little visual difference in health between treated and untreated trees. Although the reasons for the lower infestation at these sites is unclear, it may indicate that these areas do not need to be as aggressively treated as sites that have much higher levels of infestation.

  • Research Category: Invasive Plants, Pests & Pathogens