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.
- Current and Recent Hydrologic Conditions: The Loudoun County Government's Water Resources Monitoring Program collects and analyzes hydrological data specific
- Weekly Drought Map: Maps showing current and predicted drought, which can stress trees and increase wildfire risk.
- 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.
- Forest Threat Summary Viewer: Provides images, distribution maps, web links, extension and state contact information, and brief and detailed descriptions about specific forest threats in the eastern United States.
- U.S. Forest Service Pest Alerts: Fact sheets on major pests affecting forests throughout the United States.
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.
- Hemlock Woolly Adelgid: An exotic invasive insect that kills eastern (Canadian) and Carolina hemlock. Present in Loudoun County.
- Sirex Wood Wasp: An exotic invasive insect with the potential to cause significant mortality of pines. Not yet reported in Loudoun County or Virginia.
- 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.
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.