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From the ashes: How we’re confronting devastation caused by the Emerald Ash Borer


A mature ash tree full of green leaves.
A mature ash tree at Conestee Nature Preserve.

Water is one of Conestee Nature Preserve's defining features.


And where there is water in our 640 acres, ash trees are nearby. 


Take a walk on one of our low lying trails or boardwalks and look around. You’ll almost certainly see one. Scan for the tree’s distinct opposite branching, offshoots reaching symmetrically toward the sky.


If you’re lucky, you’ll come across an ash tree that’s still thriving. Unfortunately, they’re becoming more difficult to find.


The Preserve’s ash trees are in peril.


Evidence of their plight scars nearly every trunk. Examine the furrowed, diamond-shaped bark and you’ll notice the tiny marks of death: D-shaped exit holes left behind by the Emerald Ash Borer.


The invasive beetle, named for its bright metallic green color, is decimating the Upstate’s ash tree population.


The Emerald Ash Borer (EAB) made its first U.S. appearance in southeastern Michigan in 2002, but likely existed undetected in North America since the 1990s. It probably arrived in the United States on solid wood packing material carried in cargo ships or airplanes originating in its native Asia.


Since then, the Emerald Ash Borer has ravaged North America’s ash tree population. Lacking natural defenses against the borer, hundreds of millions of ash trees have fallen victim. The borer has spread in all directions, killing an estimated 99% of ash in its path.


EAB was first detected in the Upstate in 2017. Although we can’t pinpoint exactly when the borer arrived at Conestee Nature Preserve, it’s clear the beetle has been feasting on trees here for years.


It’s also apparent that the Emerald Ash Borer will fundamentally alter the Preserve’s landscape. In many ways, it already has. Dozens of skeletal dead ash trees stand beside many of our most popular boardwalks.


It’s a bleak picture, but we’re committed to ensuring the best possible future for the Preserve’s habitat.


We started by conducting an ash tree survey in the summer of 2023. It didn't take long for us to realize that Conestee Nature Preserve has a staggering number of ash trees. Awestruck arborists who have visited the Preserve consistently remark that we have more ash than they’ve seen anywhere else in the greater Greenville area.


Exceptionally resilient and versatile, ash trees thrive in our wetlands and along our stream banks. Ash trees have been labeled “ecosystem engineers” – a title they share with Conestee’s busy beavers – meaning they modify and create ideal wetland areas. Their transpiration powers keep the water table balanced and they offer crucial habitat for wildlife and humans alike, providing shade over some of our most popular trails.


How exactly does EAB wreak havoc on these magnificent trees?


It starts when female beetles lay eggs in the bark. Upon hatching, the larvae burrow into the tree, feasting between the sapwood and bark, leaving behind winding S-shaped larval galleries. By eating tissue under the bark, the EAB larvae disrupt the tree’s ability to transport water and nutrients, ultimately leading to its demise.


Once they pupate into adults, borers exit the tree through a D-shaped exit hole.


Left: A larval gallery left behind by EAB. Middle: A D-shaped exit hole in ash tree bark. Right: A grove of dead ash trees.


The countless dead and dying ash trees within the Preserve now stand as testament to EAB's devastation. To safeguard our visitors and infrastructure, hazardous ash trees lining frequented trails have been removed, while the dead trees off the trail will be left to serve as wildlife habitat.


The good news is that we still have many ash trees that haven’t yet been killed by the borer. And there’s a way to protect them from future harm.


We’ve identified several dozen ash trees, most of them visible from popular trails, that were recently treated with insecticide to kill the Emerald Ash Borer. Tree care professionals used a backpack sprayer to responsibly apply insecticide directly to the trunk of the ash trees. The trees absorb the insecticide and transport it systematically throughout its trunk and branches.


While this unfortunate but necessary intervention won't reverse damage already inflicted, it offers a chance to protect these trees from future infestations, albeit requiring ongoing treatment.


Why go to all that trouble and cost to treat trees that are already damaged?


Preserving ash trees could prove to be critical to the long term survival of the species. Although the trees we save will eventually die, they'll continue to produce seeds essential for ash regeneration, preserving genetic diversity within the ash population. Ash are dioecious, meaning there are individual male and female trees. We’ll treat both to encourage future seed production, hoping that future generations may develop natural defenses against EAB.


We can’t preserve all of our ash trees. So, we’re proactively replacing them by replanting native, site specific trees and shrubs. We’ve selected water-loving species like bald cypress, water tupelo, river birch, swamp chestnut oak, sycamore, buttonbush, elderberry, yaupon holly, and more.


This year, we’ve already planted several hundred trees and shrubs in our ash tree restoration areas. As ash trees fall, these trees and shrubs will grow to replace their habitat value.


Before replanting, we’re removing invasive species like privet that have already started to dominate the understory around ash trees.


Our multifaceted approach to ash tree management. Left: Tree care professionals remove a hazardous dead ash tree from along our trails. Middle: Volunteers from General Electric replant native trees and shrubs. Right: A tree care professional applies insecticide to a healthy ash tree.


Our efforts up to this point have largely been fueled by generous grant funding from the South Carolina Forestry Commission. While this funding has equipped us with the resources needed to accomplish early milestones, we need additional funding for our work to be sustainable over the coming years. There are still several ash tree restoration areas we plan to focus on later this year and into 2025.


To support our ash tree management plan, please visit conesteepreserve.org/ways-to-give.


While we’re optimistic the Preserve will be home to ash trees for years to come, I encourage you to take a moment on your next walk through the Preserve to appreciate the ash trees we have left.


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