Forest stand characteristics of Jefferson National Forest that observed gypsy moth defoliation from 2015-2019 in southwestern Virginia

The gypsy moth (Lymantria dispar L., Lepidoptera: Erebidae) is an invasive forest pest that has greatly impacted oak dominated forest stands in the northeastern United States. The pest, introduced in the 1860s in Massachusetts, has spread significantly north, south, and west. The National Gypsy Moth Slow the Spread (STS) limits its spread by targeting isolated, low-density gypsy moth populations with aerial applications of insecticides and/or pheromones. Other activities by state and federal agencies include conducting aerial and ground-truth surveys of forest stand injury, resulting from gypsy moth defoliation. Annually, thousands of forested acres across the Commonwealth of Virginia are defoliated by gypsy moths. This survey was conducted to compare and identify some forest stand characteristics of infested (outbreak) and uninfested (control) areas of Virginia that could be used to predict further gypsy moth defoliation. All of the research sites were located in southwestern Virginia in close proximity to the Jefferson National Forest. The survey found stand density index, proportions of defoliation per site, and total basal area per acre of preferred host trees with gypsy moth injury to be significant factors in examining forest susceptibility. This research should be continued to further analyze these forest characteristics and help predict where future stand defoliation could occur.