Forest graveyards: The science behind ash borer

Ingrid Schmidt

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Spring is a time for new life. All of the flowers begin to bloom, the birds come back after a long winter and the trees begin looking green again.

But so many trees have not sprung back to life. In fact, entire wooded areas are filled with dead trees, looming sadly overhead.

All of the dead trees have one thing in common- they are all ash trees. Something is killing all of the ash trees, burrowing under their bark, and silently destroying millions of previously healthy trees.

The emerald ash borer is an invasive species native to eastern Asia. In 2002 it was discovered in Detroit, MI and Ontario, Canada, but was found in Ohio only a year later in 2003. The adult beetle is about half an inch long, and although they nibble on the leaves, they are not the ones causing all of the problems.

The ones responsible for the destruction are the larvae. The adult beetles lay their eggs in crevices in the bark. When the eggs hatch, the larvae burrow into the bark, destroying a vital part of the tree. They destroy the phloem, which transports nutrients between the leaves and the roots. When the larvae work their way around the tree, the nutrients have no way to get from the leaves to the roots, and the roots inevitably die.

With the roots gone, it does not take long for the rest of the tree to die. Richard Stoffer, Emeritus Professor of Biology and Preserve Manager at Ashland University, said that the ash trees do not have long to live once they become infected.

“A small tree might be killed in just a couple years, a large tree may take five or so,” said Stoffer. “It’s a gradual process. You start seeing parts high in the trees that don’t have leaves, and then you start seeing shoots coming out from the trunk below that. Then that dies and then eventually the whole tree is gone.”

The dead ash trees soon become covered in vines and moss. Holes cover the outside of the rough bark. Some of the holes are from woodpeckers munching on the larvae. Others are from when the larvae turns into an adult beetle and crawls out of the bark, leaving a hole the shape of a capital D.

If one were to peel off the ash tree’s rough bark, one can see all of the wounds inflicted by the ash borer. Stoffer estimates that there are over three-million ash trees in Ohio that have been killed by the emerald ash borer.

Many homeowners and businesses have been forced to cut down and replace their ash trees. Removing trees is not just a hassle, but it can also be very costly. AU’s Grounds Supervisor, Toby White, had to get 38 ash trees cut down on campus during the summer of 2015.

“Our total bill was about $5,000. That included removal of all the trees and chipping up the brush, hauling it off of campus and also grinding out the stumps,” said White.

Businesses are not the only victims of the ash borer. Ecosystems are dependent on ash trees and their contributions to the environment.

“It basically hurts the diversity of our forests,” said Stoffer. “Because there are many other species that rely on ash, you’ve got species in the soil, you’ve got other insects and birds and so on that either have to adapt, or we lose them. So it is a long term negative impact.”

Unfortunately, there is not much people can do to prevent the ash borer from killing their trees. There are some treatments available, one being insecticides. Insecticides can be drilled into the base of the tree. The insecticides then spread through the tree, killing larvae that start to burrow in the bark.

Josh Jergens, lawn manager for Arnold’s Landscaping, said that it is an expensive treatment and the trees have to be retreated on a yearly basis.

“The cost is quite considerable for the treatments and the application,” said Jergens. “It depends on the size of the tree. The bigger it is, the more chemical you’re going to need, so that just means that the price is going to be steeper.”

After cutting down dead ash trees, it is hard to know how to dispose of the firewood. In fact, there are many federal restrictions for moving ash firewood. All infected areas are prevented from moving firewood outside of the restricted areas.

Much of the spread of the ash borer can be linked to the moving of firewood to unaffected areas.

“If you look at the early records of where the ash borer was found in Ohio, it follows the turnpike, 75 and 71,” said Stoffer. “That’s probably the principle way it is being spread, by transporting firewood.”

The ash borer is not expected to slow down on its war path any time soon. Before long, the borer may take out all of the ash trees in North America.

“The ash borer now is going south, it’s all the way to Georgia. From East to West, it’s from New Hampshire all the way out to Colorado, so in just a few years it’s going to be in every state,” said Stoffer.

The only hope for the ash tree’s survival is to find some resistant trees. None seem to have emerged thus far, but scientists are still hoping to find ash trees that are not affected by the emerald ash borer.

Meanwhile, businesses and homeowners are trying to move on from the ash borer damage. AU has made plans to replace some of the fallen trees.

“There will be some hard woods put in, some hard maples, some hard oaks,” said White. “I don’t have plans to replace all 38 trees, but we are going to be planting some other varieties of trees most of the locations.”

While looking at Ohio forests, it seems they have turned into ash graveyards- each branchless trunk a reminder of the damage caused by the ash borer. But if people look hard enough, there are still trees blooming. Dogwoods and crabapples offer the forest their beautiful flowers while oaks and maples are beginning bud.

Nature has a recovery plan, and although society may be losing the ash for good, the forests are not going down without a fight.

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