In 2009 a new and terrible threat entered Kentucky; the Emerald Ash Borer (EAB), Agrilus planipennis. This terrible, exotic beetle is true to its name, featuring emerald green wings. While they are more recognizable as adults, it is during the insect’s larvae stage that it causes the most damage, boring into living ash wood killing the entire tree.
Discovered in northern Michigan in 2002, the Emerald Ash Borer has devastated our forests and urban ash trees on a scale similar to how our native American Chestnut and Eastern Hemlock were affected in the last century.
Only noticed to attack white and green ash trees (Fraxinus americana and F. pennsylvanica), the young larva bore through the living tissue of the tree (just beneath the bark), then emerge as adults through a small 1/5 inch “D” shape exit hole. This feeding kills the tree by cutting off the transportation of fluids and sugars along the trunk. So far, it has not been noticed to affect blue ash (Fraxinus quadrangulata).
There are several bright to dark green insects that are often confused with the EAB. Even though they have no close relation, I relate the look of EAB to tiny, metallic green grasshoppers missing their jumping legs. Emerald Ash Borers are 1/2-inch or less long (shorter than a small paperclip) and very slender, with the blunt head tapering to the end of the abdomen. The wing covers are emerald green; the top of the abdomen, visible when the wings are spread, is actually metallic purple-red.
Newly emerged adults are most active when it is warm and sunny. One female will lay between 60 and 90 eggs.
Unfortunately, a tree with noticeable infestation that is dying cannot be saved. Trees in good health, without insects, can be treated by a qualified technician; however, treatment can be expensive and needs to be done on a routine 2 to 3-year cycle in May to early June.
At The Parklands of Floyds Fork, we have taken a multi-level approach to our ash tree management. We first properly identify the tree as blue ash or white/green ash. In high use areas along roadways and trails, we remove the infected ash trees to avoid sudden falls that could harm visitors. This removal was very noticeable in Broad Run Park as the forest has a high ratio of ash trees along Broad Run Parkway and the Louisville Loop, which called for a proactive approach of removal for public safety.
Damage from the Emerald Ash Borer can be seen on the inner bark of this ash tree located near Limestone Gorge in Broad Run Park
Sometimes we will remove the top of the tree, leaving a 10’ or slightly taller snag, which is a safe height that provides ample wildlife benefits. (The dead tree does not support EAB as it only lives on living trees.) In a few select areas we are using chemical treatment on green and white ash trees to preserve this species in the parks. In deep, forested areas we are leaving the ash trees as they either succumb, survive, or get replaced by a succession of native tree species.
EAB is an unfortunate problem that is affecting our wild and cultural landscapes, causing us to lose a dominant species in our forest and beautiful trees in our home communities. Being responsible in timely management (removal or treatment) will promote a safe environment until we are able to better manage the EAB problem. Hopefully, one day we will enjoy the return of this important native tree.
University of Kentucky College of Agriculture – http://pest.ca.uky.edu/EXT/EAB/welcomeeab.html
U.S. Forest Service – http://na.fs.fed.us/fhp/eab/
Emerald Ash Borer Information Network – http://www.emeraldashborer.info/
Hungry Pests (USDA) – http://www.hungrypests.com/the-threat/emerald-ash-borer.php
About the Author
Tom is a seasoned professional with two decades of experience in horticulture, botanic gardens, conservation, and organic landscaping. He holds a master’s degree in urban horticulture from the University of Washington in Seattle, WA. He has worked for established institutions such as the University of Washington Botanic Gardens in Seattle, WA and New England Wild Flower Society in Framingham, MA. Tom’s most notable work has been leading the management of horticulture at newly urban designed parks starting with the Rose Fitzgerald Kennedy Greenway opened in 2008 in downtown Boston, MA built on top of the infamous “Big Dig”. Most recently, Tom served as Horticulture Director at the High Line, a public park in New York City along unused, elevated train rails. He recently joined 21st Century Parks in Louisville, KY as Horticulture Director involved in the newly-built model urban park at The Parklands of Floyds Fork. He is committed to the preservation of our cultural landscapes through sensible design, horticulture practices and public education.