Emerald Ash Borer

Emerald Ash Borer

The emerald ash borer is a serious invasive insect that, prior to Maryland's detection in late August 2003, had only been detected in the U.S. in Michigan (2002) and Ohio (2003). The insect feeds on and kills ash trees, an important neighborhood and landscaping tree, one to three years after infestation.

To help control the spread of this dangerous beetle, Maryland citizens and visitors are being asked to comply with the established quarantine and refrain from transporting firewood from the infested area in Prince George’s County to any other area AND from other states into Maryland.

If you suspect EAB infestation, please report it through the Ask Maryland’s Garden Experts link at http://extension.umd.edu/learn/ask-gardening.


The Maryland Department of Agriculture (MDA) detected the insect during a routine nursery inspection in late August, 2003.

Ash trees infested with Emerald Ash Borer (EAB) were received at a registered nursery and landscape business in Brandywine in Prince George’s County. Nursery records and regulatory investigation by MDA and the USDA indicated the nursery received 121 ash trees from Michigan in two shipments (57 on April 2 and 64 on April 3).

The Maryland nursery had ordered the trees from Tennessee. Unbeknownst to the Maryland nursery, instead of filling the order, the trees were ordered by the Tennessee nursery and direct shipped from Michigan to Maryland. After receipt, adult beetles emerged on site at the nursery and these beetles subsequently infested other ash trees at the nursery.

All but three of the 121 trees from Michigan are believed to have been accounted for and destroyed. MDA removed from the nursery an additional 389 ash trees that were exposed when the beetles emerged and began laying eggs. Of these 389 trees, 71 were found to contain EAB larvae.

Quarantine map

In an attempt to eradicate the beetle before it could spread further, MDA identified and removed ash trees within one-half mile of the nursery. MDA also established numerous “trap” trees in the area that were checked regularly for evidence of EAB.  In August, 2006, MDA rediscovered EAB on ash “trap” trees. State and federal quarantine orders were issued for all of Prince George's County in 2006 and revised in 2007, and in 2008 to include Charles County. About 42,000 ash trees were removed on nearly 17,000 acres over several years. There were five main aspects of the EAB action plan for accomplishing this pest control action:

  • Identification, flagging and mapping of all ash trees in the environment within 2 miles.
  • Cutting and removal of identified trees.
  • Staging, stripping, chipping and disposal of cut trees.
  • Follow–up surveys to detect any first generation beetles in 2007.
  • Public communications and outreach efforts.

In 2009, Maryland determined that new EAB detections had shown an "edge effect" suggesting that cutting was somewhat effective, but not enough to stop EAB completely. With guidance from the National EAB Science panel, the state directed efforts away from eradication through wholesale removal of the ash resource, and now focuses on survey, insecticide treatments, and releases of natural enemies in the project area in order to reduce populations and prevent the spread of EAB.

Maryland began releasing the approved biocontrol agents, three species of wasps that are parasitoids specific to EAB.  Intensive trapping was established to better track spread and the quarantine remained in place.  In 2011, EAB was detected in several more counties, Anne Arundel, Howard, Allegany, and Washington (map in Appendix A).  The spotty distribution suggested that the rapid spread was due to human-aided transport.  University of Maryland research found that natural spread from the original point of infestation was less than 1 mile per year initially, but over time increased exponentially, suggesting that either EAB could fly further than originally believed, or that humans moving infested ash products promoted a more rapid expansion.

Maryland currently has a quarantine in place for all counties west of the Chesapeake Bay (Order #11-02, effective July 11, 2011).  The current quarantine is kept posted on the MDA website at http://mda.maryland.gov/plants-pests/Pages/eab.aspx.  This quarantine applies to all of Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles, Frederick, Garrett, Harford, Howard, Montgomery, Prince George’s, St. Mary’s, Washington counties and Baltimore City, Maryland. This action aims to limit the spread and keep EAB from crossing the Chesapeake Bay and being introduced to the Eastern Shore. It allows the movement of wood within Maryland west of the Chesapeake Bay but limits transport of wood without a permit onto the Eastern Shore, where no EAB has yet been found.  The quarantine applies to:

  • the emerald ash borer,
  • firewood of all hardwood (non-coniferous) species, including any piece thereof;
  • nursery stock,
  • green lumber,
  • other material living, dead, cut, or fallen, (e.g. logs, stumps, roots, branches) of the genus Fraxinus, including any piece thereof, and
  • uncomposted ash chips and uncomposted ash bark chips larger than 1 inch in diameter in two dimensions.

The APHIS quarantine regulates transfer of ash material across state lines, and effective April 1, 2012, will allow movement of material within a large multi-state quarantine zone.  This quarantine will support greater opportunities for utilizing ash wood within the regulated area, and keep federal regulatory activities at the edges of the infestation where they can have the greatest effect.  To avoid spreading EAB more rapidly, basic precautions such as not moving firewood and not planting new ash trees should be practiced even within the quarantine zone.


To help Maryland better plan for a future that minimizes adverse effects of the emerald ash borer, a revised plan has been drafted.  The Maryland Emerald Ash Borer Long-term Management Plan is open for comment until April 23, 2012.  Please send comments to Anne Hairston-Strang at MD DNR Forest Service, 580 Taylor Ave., E-1, Annapolis, MD  21401, phone 410-260-8509, fax 410-260-8595, email anne.hairston-strang@maryland.gov.


Marks left by the Emerald Ash Borer

Emerald Ash Borer adults are dark metallic green, one-half-inch in length and one-sixteenth of an inch wide. They are present only from mid-May until early August. Larvae are creamy white in color and are found under the bark. (See links below for photos.)

Affected trees show symptoms of infestation including: die-back on the upper third of the tree, D-shaped exit holes in the bark where adults emerge, vertical splits in the bark, and distinct serpentine-shaped tunnels beneath the bark in the cambium, where larvae effectively stop food and water movement in the tree, starving it to death. It takes 1-3 years for the infested tree to die.


The greenhouse and nursery industry is the second largest agricultural industry in Maryland, accounting for more than $360 million in cash receipts. (Source: Maryland Agricultural Statistics Service, Farm Receipts in 2004)

Ash trees are one of the most common landscaping trees used in the U.S. and are common in western Maryland forests. Ash wood is used for all traditional applications of hardwood from flooring and cabinets to baseball bats.

Ash is the most common tree in Baltimore accounting for 293,000 trees -- 10.4% of the city’s total tree population. Ash accounts for 6 to 6.5 million trees in the Baltimore metro area. USDA has estimated losses could exceed $227.5 million in the Baltimore area alone.


Please report it at http://extension.umd.edu/learn/ask-gardening.


Information from the Department of Agriculture

How to Detect and Diagnose Infestations of Emerald Ash Borer

Quarantine Order

Quarantine Map and Current EAB Locations