Treat Your Ash Trees Now to Protect Them From the Emerald Ash Borer

June 1, 2011

More Information

epicormic shoots
Epicormic Shoots

bark splitting
Bark Splitting

Fairfax Trapping Area
Fairfax Trapping Area

Emerald Ash Borer Video
Emerald Ash Borer and Firewood Quarantine Video video icon

Homeowners who wish to protect their ash trees from the emerald ash borer should take action in June, say county officials. Every ash tree is at risk from this insect because it has been found across the county.

Many healthy or infested ash trees can be treated with an insecticide available at many garden stores. Look for any insecticide that contains the chemical imidacloprid.

For trees with trunks greater than 15 inches in diameter, homeowners should seek treatment from a professional tree care firm. They can inject the chemicals directly into a tree's trunk which will last longer than other treatments available to the public.

If a tree has lost more than 50 percent of its leaves, insecticides most likely won’t work, and there are no other treatment options.

Insecticides are most effectively applied in May through June because trees are more likely to absorb the chemicals as they revive in spring. It takes four to six weeks for the insecticide to be thoroughly distributed within the tree. Insecticides available to homeowners must be reapplied once a year, and professional treatments need to be repeated once every one to three years, depending on the insecticide used.

Two signs indicate that an ash tree may be infested with the emerald ash borer:

  1. Trees may have horizontal splits or fissures in their bark
  2. Trees may have small shoots or branches growing from the trunk, called epicormic shoots.

To track the insect’s spread, approximately 500 glue traps were hung in ash trees across the county as part of a statewide monitoring program.  The large, purple, triangular traps are non-toxic. They don’t contain pesticides or chemicals. To date, this pest has been found in Arlington, Fairfax, Frederick and Prince William counties.

Officials ask the public to report traps that have fallen to the ground, and advise not to touch them since they are covered with extremely sticky glue. To report fallen traps, call the Fairfax County Forest Pest Branch at 703-324-5541, TTY 711.

State and federal quarantines ban the transport of firewood outside of most of Northern Virginia to prevent this pest from spreading to other parts of the state. The quarantine covers:

  • Fairfax County
  • Arlington County
  • Clark County
  • Fauquier County
  • Frederick County
  • Loudoun County
  • Prince William County
  • cities of Alexandria, Fairfax City, Falls Church, Manassas, Manassas Park and Winchester.

However, firewood may be transported within the quarantined areas.

The emerald ash borer was discovered in Fairfax County in 2008. These insects have killed more than 25 million ash trees in the U.S. The borers are native to China, Korea and Japan, and they first arrived in this country from Asia in the 1990s.

For more information about the emerald ash borer, effective treatments or the trapping program, contact the Fairfax County Forest Pest Branch at 703-324-5541, TTY 711 or by e-mail.


Get News. Get Information. Get Fairfax County.Contact: Merni Fitzgerald, Director, Office of Public Affairs
703-324-3189, TTY 711, Media Pager: 703-324-NEWS (6397)
To request this information in an alternate format, call 703-324-3187, TTY 711

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