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Threats to Trees and Forests
 Photo of tree killed  by Emerald Ash Borer
Green ash killed by EAB showing 
D-shaped exit holes 
(Photo by David Roberts, Michigan State University)
Throughout Loudoun County, there are a number of potential threats to trees in forests and in urban areas. These include pests and diseases, invasive plants, wildfires, and extreme weather events.

  • Current & Recent Hydrologic Conditions: The Loudoun County Government's Water Resources Monitoring Program collects and analyzes hydrological data specific
    to Loudoun. 
  • Weekly Drought Map: Maps showing current and predicted drought, which can stress trees and increase wildfire risk. 

Forest Fires
  • Firewise: A community program to reduce the risk of wildfires to your home and community. 
  • Fire Danger Rating Map: A U.S. Forest Service map showing current wildfire risk 

Pests and Diseases

Pests of Serious Concern 
The following tree pests pose a serious threat to trees in Loudoun County, and can severely weaken or kill affected species:

Diseases of Serious Concern
  • Beech Bark Disease: Can cause stand mortality and disfiguration in American beech. Not yet reported in Loudoun County, but has been identified in Highland County. 
  • Oak Wilt: Affects many species of oaks. 
  • Sudden Oak Death: A disease that kills oaks and other trees. Not yet reported in Loudoun County or Virginia.
  • Thousand Cankers: Affects and kills black walnuts. Fairfax and Prince William counties are currently under quarantine.

Invasive Plant Species
Plants introduced from other areas without native predators, can outcompete and displace native species. These plants can increase fire risk, reduce the health and value of trees, and reduce the quality of wildlife habitat.

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