The Green Menace

The Green Menace
Photo: Pest and Diseases Image Library,

ANNAPOLIS, MD (January 3, 2007) – Twenty million ash trees are dead and gone. Stately trees with high canopies covering miles of neighborhood streets are gone; the shaded avenues now denuded of green. In the forest, majestic giants have been brought down by a small green inconspicuous beetle. So inconspicuous, in fact, that researchers now believe that this beetle had been expanding its deadly impact for as much as 10 years in the Detroit, MI area before entomologists in 2002 finally put a name on what was killing first hundreds, then thousands of ash trees: the emerald ash borer, Agrilus planipennis. Because of the huge threat EAB poses to ash species, important trees in our forests and yards, the EAB has been chosen as the Maryland Invasive Species Council’s Invader of the Month for January 2007.

Thought to have arrived in North America in solid wood packing material from its native Asia, the emerald ash borer (EAB) provoked a rapid response. Officials quickly established quarantines around the Detroit area. With funds and involvement from the US Department of Agriculture, state and local agencies intensified surveys, and began aggressive eradication efforts in an attempt to contain the problem. Yet despite these measures, a Michigan nursery evaded the quarantine and shipped ash trees into Maryland in the spring of 2003. Unseen underneath the bark of the Michigan trees were the larvae of the EAB, which developed into the beetles and emerged that summer, before the infested trees were discovered in August 2003 by the Maryland Department of Agriculture (MDA). After the discovery, MDA coordinated an extensive, well-organized, multi-agency emergency response to the EAB and it was believed that the insect had been eradicated by spring 2004. Then, on August 15, 2006, EAB was discovered here again near the original site in Prince George’s County.

The Green Menace
Emerald ash borer adult, in tunnel. Photo: Eric R. Day, Virginia Polytechnic Institute and State University,

Adult beetles are bright metallic green with rounded bellies and flat backs, one-third to one-half inch long. They emerge in the spring and lay eggs on the bark of ash trees. The creamy white larvae hatch and move into the cambium layer. They live most of the year under the bark of ash trees, feeding on the tissue that carries food and water up and down the tree, effectively girdling the tree and starving it to death. Infested trees show symptoms within a year. The upper third of a tree dies back first, followed by the rest the next year. This is followed by many shoots or sprouts emerging below dead portions of the trunk. The canopy continues to decline until the tree eventually dies. Fortunately the EAB attacks only ash trees (genus Fraxinus), unfortunately infested trees always die. Once a tree is infested, controls, including insecticides, are not able to completely rid the tree of the borer larvae.

A federal quarantine for emerald ash borer is now in effect over the Lower Peninsula of Michigan and all of Ohio, Indiana, and Illinois. These states also maintain interior quarantines to prevent intrastate spread of this pest. The Maryland Secretary of Agriculture issued a Quarantine Order on August 21, 2006, restricting the movement of all ash wood and nursery stock and all hardwood firewood from the County. A massive cooperative eradication effort involving federal, state and local officials, private contractors, public utilities, landowners, and business people is again underway. In 2004, the MDA, with support from the US Department of Agriculture, Animal Plant Health Inspection Service (APHIS), the Maryland Department of Natural Resources (DNR), and many others, destroyed more than 1100 ash trees on 500 acres in a ½ mile buffer around the nursery where the infested trees arrived. The MDA also identified and removed all ash trees transplanted into other areas by landscapers. This time more than 11,500 acres are impacted. Eradication must be completed by the end of March, 2007, before adult emerald ash borers emerge and infest more ash trees.

What is at stake if the emerald ash borer isn’t stopped? – In Maryland, ash is the most common street tree in Baltimore, making up about 10% of total trees. Ash accounts for over 3% of trees in naturally wooded area in Baltimore and surrounding counties. USDA has estimated that losses could exceed $227,500,000 in the Baltimore area alone. The Maryland DNR also estimates that about 20% of our riparian trees, vital to the health of the Chesapeake Bay, are ash trees. USDA estimates that at the national level, if the emerald ash borer went unchecked in the lower 48 states, the undiscounted loss could range from $20 – $60 billion dollars. Ash wood is used for all traditional applications of hardwood from flooring and cabinets to baseball bats.

The emerald ash borer threatens to kill all ash trees in Maryland and ultimately the United States if not stopped. Maryland is the most distant, and only non-contiguous, of the infested states. Many exotic pests such as the emerald ash borer, which doesn’t move much farther than ½ mile per year on its own, can be carried on infested wood by humans hundreds and even thousands of miles to new areas.

Stopping the spread of the emerald ash borer will take more than regulations. The emerald ash borer, which doesn’t move much farther than ½ mile per year on its own, can be carried by humans hundreds of miles to new areas in infested wood – most commonly firewood. Everyone can help! Be an ambassador by watching for and reporting symptoms, not moving ash wood, and spreading the word about the quarantine and the perils of moving hardwood firewood.

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Pennsylvania Department of Conservation and Natural Resources – Forestry ,
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Photo: Jared Spokowsky, Indiana Department of Natural Resources,

For more information about the emerald ash borer and the Maryland quarantine and eradication program, visit the national coordinated emerald ash borer Website, and click on the “Maryland” link, or go directly to

"Don't Pack Firewood – Buy it Where you Burn it"

For more information about other Invasive Species of Concern, visit the Maryland Invasive Species Council.