Since its arrival in Michigan in 2002, the emerald ash borer (EAB) has killed over 100 million ash trees in North America, causing substantial ecological and economic damage. The dark green beetle is a mere half inch long, but the tunneling of its larvae under ash bark can kill a tree in just two to four years.

With the discovery of EAB in Pennypack Park this summer, Philadelphia news media has been buzzing with concern. Is the city prepared? What should homeowners do? Will any ash trees survive?

The same street in Toledo, Ohio, in 2006 (before EAB) and in 2009 (after EAB). (Photo credit: Daniel Herms,

The first question can be answered easily: Yes. The City of Philadelphia developed an EAB Management Plan in 2012, and its implementation is in full swing. The Philadelphia Department of Parks and Recreation (PP&R) surveyed ash trees, evaluating their current health and hazard potential. Using this information, and with the goals of conservation and public safety, they determined whether each tree would be preemptively removed, treated with insecticide, or left alone. Over 1000 ash trees will be treated for resistance against EAB, and many of the ash trees removed will be replaced with other native tree species.

Many private parks and arboreta in “America’s Garden Capital” have similar management plans in effect. The Morris Arboretum’s ash collection was evaluated based on forest canopy impact, and selected trees are being treated every two years. It is not known how long the EAB invasion will persist in the region, but both the PP&R and private gardens are preparing to treat ash trees for at least the next ten years.

However, this still leaves thousands of other ash trees to be considered… Yours! The homeowners of Philadelphia could make or break the city’s collective response to the EAB invasion. All things considered, the best options are to pre-emptively remove ash trees or treat with insecticide. Over 99% of ash trees will be affected by EAB, and once a tree has been killed it becomes much more dangerous and expensive to have it taken down. Since EAB was just discovered within the city limits, it’s the perfect time to consult a local arborist and consider the options for any ash trees on your property.

In addition, the Morris Arboretum has several special events to help the community prepare. On September 29th is a Tree Injection Technology Workshop, discussing the most popular method for ash treatment. At the Tree Canopy Conference on October 13th, speakers will cover many crucial topics in urban forestry, including EAB management at Fairmount Park. Check out our online course listings to learn more.

The emerald ash borer will undoubtedly have a big impact on Philadelphia, but if public understanding of the issue increases and everyone follows through with management plans, some ash trees might just survive.

Two adult emerald ash borers, shown next to their D-shaped exit holes. (Photo credit: Total Landscape Care,

Online EAB resources: