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Emerald Ash Borer

What is the Emerald Ash Borer?

A small insect originally from Asia, the Emerald Ash Borer (EAB) was introduced to the U.S. through imported lumber and has spread across North America over the last 15 years, leaving behind tens of millions of dead ash trees. The decline of an infected ash tree can be rapid (1-4 years) and EAB appears to kill nearly all native ash trees. The borer has been verified in nearly every county in Pennsylvania, including Lancaster County. Its arrival in all of the City’s ash trees is imminent.

The EAB spends its infancy as a larva in the tree bark, not unlike a worm in soil, then it changes into a half-inch-long green beetle that exits the tree and flies off to another ash tree. 

What is an Ash Tree?

Common to the Northeastern forest region of North America, ash trees have been a standard deciduous shade tree in many municipalities and backyards for decades due to their beauty, shade, and hardiness to urban conditions. These trees have bark that changes from smooth to diamond-shaped as they age. They also have compound leaves of 5-11 leaflets. Their branching pattern is opposite, meaning that branches, leaves, and leaflets form in pairs at the same points on a branch; they don’t alternate from one another.

For more information on how to identify an ash tree, see Penn State University’s Ash Tree ID Guide.

How do I tell if my Ash tree is infected?

Signs of an EAB infestation include small D-shaped exit holes, leaf dieback, woodpecker damage, scarring from larvae, and new shoots coming from the base of the tree (epicormic shoots). When the beetles exits the tree, they leave small holes in the bark. A tree affected by dieback will lose its leaves in large bunches, mainly from the top down. Woodpeckers typically leave behind round holes that cause the surrounding bark to fall off. The presence of larvae can be evidenced by s-shaped, white-colored channels in the wood immediately behind bark.

For visual representations of these symptoms, see Michigan State University’s Guide to EAB Signs and Symptoms.

What should I do if I have an ash tree?

You have three options: (1) You can treat the tree with an insecticide that targets EAB. Refer to this manual for information on insecticides: Insecticide Options for Protecting Ash Trees from Emerald Ash Borer; (2) You can remove the tree and replant it before it becomes infected and hazardous; (3) You can do nothing; however, this is a risky option. It is not always immediately obvious when the tree becomes infected. Moreover, it is difficult to reverse the decline of infected trees with insecticides. Hazardous trees can also be more expensive to remove.The ash tree will probably begin declining in the next few years since EAB has already been verified in Lancaster County.

If you have an ash tree along a public right-of-way (e.g., a street or alley), please contact the City Arborist to discuss treatment or removal and replanting: jbower@cityoflancasterpa.com or 717.291.4846. If you have an ash tree on your private property and not in a public right-of-way, then please consult a local arborist for treatment options. ALL tree work requires a permit from the City Arborist. Refer to the City Tree Ordinance for more information.

How many ash trees are in Lancaster?

Before the threat of Emerald Ash Borer, Lancaster City contained approximately 282 known ash trees – 191 were in parks and 99 were along streets. Together, they accounted for roughly 3% of the trees in parks and on streets. Many of these trees have already been removed and replanted or treated. It has been estimated that at least another 100 exist on private property and in sections of the City without a tree inventory.

Why should I deal with my ash tree now?

Dead and dying trees of any species or age pose a threat to nearby property, possessions, and people. Ash trees become especially brittle when they begin to decline in health. The Emerald Ash Borer will very likely kill all of the ash trees in Pennsylvania. It will be safer and cheaper for landowners to treat ash trees or remove them before they become hazardous. Please consult a local arborist.  

What is the City Doing About EAB?

In 2014 the City adopted an Emerald Ash Borer Management Plan to develop a strategy for mitigating hazardous ash trees and estimating costs for removal, replanting, and treatment. The Lancaster Department of Public Works is acting to reduce costs and maintain quality of life by selectively treating now-healthy ash trees, and removing those that are too unhealthy or too small to be treated. All City ash trees along streets that were removed were replaced 2 for 1. In other words, about 72 ash trees were removed from streets, and the City has already planted 150 street trees.

As of July 2016 the City has removed about 90 ash trees and treated 12 others in public parks. Additionally the City, PPL Electric, and private landowners have removed about 72 trees in rights-of-way and treated about 30 others. The remaining ash trees await to be treated or removed, while another dozen that exist in natural woodland areas will be left to die in place. In partnership with the Lancaster County Conservancy, the City is actively working to increase tree canopy and increase plantings. To learn more about the City’s tree planting efforts visit the Tree Planting page.