Invasive Insects Threatening DC’s Ash Trees

Arborists from the District Department of Transportation’s Urban Forestry Administration (UFA) recently discovered a number of small, invasive beetles that pose a threat to some trees in the District.

The emerald ash borer and its “D” shaped exit hole. Photo by Phil Nixon/University of Illinois.

The emerald ash borer and its “D” shaped exit hole. Photo by Phil Nixon/University of Illinois.

Adult emerald ash borers (EABs, aka Agrilus planipennis) were found inside ash trees near Oxon Run in Ward 8 and were sighted in other locations throughout the District, which UFA has identified on an interactive map.

The larvae of these insects, which are native to China, grow and devour the insides of ash trees before chewing their way out through telltale D-shaped tunnels. Currently, the District has 215 ash trees in public space (that is, street trees); however, there are hundreds–if not thousands–of ash trees located on private property.

How to Identify Emerald Ash Borers

EABs can be identified two ways: using unique characteristics of the beetle and/or evidence of its activity in ash trees. The beetles are about a ½” in length and are a brilliant metallic green color. The larvae can range in size from 1″ to 1 ¼” and have a large, flat head and bell-shaped body segments. Please consult with online guides for proper identification. Evidence of EAB activity is observed in the bark as D-shaped holes, 1/8” in length, and winding tunnels under the bark. Light patches on the tree trunk and branches indicate areas where woodpeckers have removed bark as they search for EAB larvae. Symptoms of EAB infestation are dead/dying branches, a thin canopy, and abnormal sprouting growth along the trunk of ash trees. Unfortunately, many of these symptoms are only apparent in the late stages of EAB infestation. Once EAB symptoms are observed, ash trees decline for 2-4 years until death.

A white ash tree, in its fall and spring incarnations. Illustration by Robert O'Brien.

A white ash tree, in its fall and spring incarnations.

Impact on District Ash Trees

EABs may impact trees in the District on both public and private property. UFA is surveying ash trees in public space for evidence of EAB activity, and infested trees will be treated or removed. Many ash trees on private property may be at risk of infestation due the combination of EAB populations in neighboring states and the strong flight capability of EABs (female EABs are capable of flying 1 mile per day).

What To Do If You Have Ash Trees

For more information, please contact UFA by calling 311 or visiting 311 online. Please note that you are requesting the inspection of an ash tree.

-State Forester for the District of Columbia

 

About DDOT Blogger

The District Department of Transportation (DDOT) develops and maintains for the District of Columbia a cohesive sustainable transportation system that delivers safe, affordable, and convenient ways to move people and goods - while protecting and enhancing the natural, environmental and cultural resources of the District.
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