Threats to Trees & Forests

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.

Weather

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 & Diseases

  • Diagnosing Plant Problems: A systematic process for identifying problems with trees and other plants.
  • Loudoun County Master Gardeners: Trained volunteers who can help identify common pests and problems with trees and ornamental plants.
  • Don't Move Firewood: Prevent the spread of insects and diseases that could devastate Loudoun's forest resources by always buying firewood locally.
Green ash killed by EAB showing D-shaped exit holes

Green ash killed by EAB showing D-shaped exit holes

(Photo by David Roberts, Michigan State University)

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:

  • Asian Longhorn Beetle: An exotic invasive beetle that kills a variety of hardwood species. Not yet reported in Loudoun County or Virginia.
  • Emerald Ash Borer: An exotic invasive insect that kills ash trees, and has been identified in Northern Virginia. Virginia is now under federal quarantine, and it is illegal to move ash logs, ash firewood, or ash nursery stock out of Virginia.
  • Gypsy Moth: An exotic invasive moth that defoliates hundreds of species of plants, but oaks and aspens are most common. Loudoun County is currently under quarantine.
  • Southern Pine Beetle: A native beetle that can kill groups of pine trees that have been stressed by drought or other factors. Present in Loudoun County.
  • Spotted Lanternfly: An invasive species found in many mid-Atlantic states and neighboring counties in Virginia. Some areas are under quarantine. 

Diseases of Serious Concern

  • 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.