The Emerald Ash Borer – Planning for this Unwelcome Visitor
Written by Jeff Feaga, Office of Sustainability and Environmental Resources
Photo courtesy of Wisconsin's Emerald Ash Borer Information Source
It’s inevitable – expect the emerald ash borer (EAB) to infect ash trees in your hometown. Since its discovery in 2002 in southeastern Michigan, and its subsequent transport to Maryland in 2003 via infected nursery stock, the EAB has spread across 22 Midwestern and Eastern states (USDA EAB Distribution Map). Unfortunately, the EAB is particularly good at what it does: flying throughout the ash canopy as adults and laying eggs on the tree so that their pupae can feed on the inner bark and complete their life cycle. Ultimately, billions of ash trees in the United States will perish due to the EAB.
Emerald ash borer adult. Photo UMD Extension.
Although Frederick County has a less dominant ash tree component in our forests than many Midwestern and Northern states, our community is not immune to the EAB invasion. Ash trees are present in Frederick County as native woodland trees as well as trees planted in neighborhoods and city streets! If you have ash trees on your property, being proactive about what you plan to do with these trees before or during the onset of the EAB infestation will save you headaches down the road. Trees infested with EAB notoriously die within two or three years, causing the tree to become quite dry and brittle. These brittle conditions result in the tree being very difficult and costly to remove safely.
Dealing with the die-off of so many ash trees will be a challenge, but deciding on an appropriate response is important and can have other environmental implications. The University of Maryland Extension Service recommends early planning, and has created a thorough EAB online video that discusses the insect’s biology and gives recommendations for management. If there are only a few ash trees on your property, and they do not pose a safety risk to people or structures, they may be left to nature. Maybe the woodpeckers will temporarily enjoy them before they fall safely to the ground. Alternatively, if you have a woodlot with a potentially marketable crop of ash trees, you may want to plan a harvest. Start soon though; planning a harvest can take several years because it requires key activities such as developing an approved management plan and procuring a licensed forester. See the Frederick County Forestry Board for more information on harvesting trees. Forestry activities have the potential to cause negative secondary impacts such as soil erosion, waterway damage, or higher susceptibility to undesirable plant invaders. Therefore, attention to detail while developing and executing the harvest plan is a must.
For those people or communities that just cannot stand to imagine life without their favorite ash trees, there are some insecticides that have been successfully used to fend off the EAB. Information developed by multiple states describing the options available for ash chemical treatment can be found here. These treatments are most successful when they begin while the ash tree is still relatively healthy. The most effective treatments are systemic insecticides, that is, they are injected into the tree and deliver the chemical throughout the tree. Chemical management for EAB in ash trees can be expensive and requires multiple treatments; however, in some cases of particularly large or precariously-placed urban trees, treatment costs can actually be lower than removal costs. Studies have been completed on the potential effects of systemic insecticides on favorable insects, birds, and water resources, with initial findings indicating minimal impact. However, use of any chemical use has its risks and should be considered in the planning process.
The story of the emerald ash borer’s spread is a sad one. When faced with challenge, it is best to be proactive. Maybe it is finally a good time to construct that rustic ash wood table and bench that you’ve been designing in your woodshop all these years?
Typical ash tree on Market Street, Frederick County, MD. July 2014.