As Louisville begins to confront an urban tree canopy decimated by drought and storms, another hazard is poised to do even more damage. Emerald ash borers are invasive beetles that attack ash trees; if the trees aren’t treated, the pest could wipe out most or all of Louisville’s ash trees. But the city still lacks a comprehensive plan to combat the insect.
It’s a cool summer morning in Cherokee Park. Jacob Trader is sitting next to a huge ash tree—about 100 feet tall—on the edge of the park. He drills a hole in a root flare, then gently taps in a small plastic port. Limbwalker Tree Service co-owner Chris O’Bryan is watching.
“And the root flare is sort of like the exchange highway system for the fluids in the tree,” O’Bryan explains. “It helps distribute the chemical evenly throughout the entire canopy.”
Trader and O’Bryan are getting ready to inject chemicals into the tree to protect it from emerald ash borers. The invasive pest has been in Kentucky for about four years, and over the next few years arborists worry it has the potential to kill most, if not all, of Louisville’s ash trees. And for a city with a tree canopy that’s about 17 percent ash trees, that’s a big deal.
“The emerald ash borer is killing in the billions of ash trees, probably upwards of eight billion ash trees in the United States, and it’s killing every ash tree,” O’Bryan said. “It’s a very quiet problem, but it’s an overwhelming problem.”
Louisville already has a dearth of trees. Trees sequester carbon dioxide, reduce storm water runoff and help mitigate the urban heat island effect—which researchers have said is worse in Louisville than anywhere else in the country.
But Louisville still has no comprehensive plan to deal with the emerald ash borer, and the potential loss of one out of every six trees.
A lot of that has to do with money. It would cost about $500 to treat the huge tree in Cherokee Park, though the tree service is donating this injection. Smaller trees cost less, but the whole process has to be repeated every two years. But if trees aren’t treated, they will likely die.
Lee Townsend is an entomologist at the University of Kentucky’s College of Agriculture. He says the pest will be expensive—whether the city and homeowners decide to treat their trees or not.
“It’s expensive to treat for the emerald ash borer, but it also becomes much more expensive to take out dead trees and to remediate, to plant a new tree in or deal with the damage that might occur,” he said. “I think it’s very important to try to be as proactive as possible when dealing with this insect.”
But right now, Louisville’s response to the emerald ash borer is piecemeal.
The Waterfront Development Corporation has treated all the ash trees in Waterfront Park—they estimate 5 percent of their trees would be gone without any action.
Metro Parks is trying to treat as many trees as possible in the city’s parks, and along the Olmsted Parkways. In the past three years, using money garnered from the parks budget, state grants and the Olmsted Conservancy, the department has only been able to treat about 20 percent of the ash trees on parks property. And those trees will need repeat treatments every one to two years.
Some neighborhood associations have taken action, requesting money from council members or fundraising to inoculate trees in the city right-of-ways. The Cherokee Triangle Neighborhood Association treated 23 ash trees this spring, spending about $3300 of the association’s profits from the annual art fair.
But most of the ash trees on city right-of-ways and easements, or trees on Metro Government-owned property are so far unprotected.
“We’re not able to inoculate our trees for the emerald ash borer,” city arborist Mark White said. “We do not have the funds for it at this point in time.”
White says so far, the only official action has been to try to educate residents about how to protect their ash trees, and to remind them they’re responsible for trees on public right-of-ways near their home. If the trees are allowed to die, besides the environmental detriment, they’ll pose a safety issue to people and property and will have to be removed.
Katy Schneider is the co-chair of the Louisville Metro Tree Commission.
“Something needs to be done,” she said. “We just don’t have the resources to do anything about it. We don’t know where the trees are, we don’t know how many ash trees there are.”
Schneider says the first step in getting a coordinated city response to the emerald ash borer would be to take an inventory of the city’s trees. That’s expensive too, but she’s hopeful that Metro Council will approve a new position in next year’s proposed city budget: an urban forester. That person could help coordinate efforts to combat the emerald ash borer.
But this is a time sensitive issue. The trees really need to be injected before they show signs of infection. Once the insects begin to attack the tree and it starts to die, it’s often too late.
Back at Cherokee Park, Chris O’Bryan and Jacob Trader from Limbwalker are finishing up the ash tree injection. They attach pressurized bottles of the insecticide to the tree via tubes. It’s very medical looking…like a tree I.V.
After this ash tree absorbs all of the treatment, it’s protected for two years. But this is a very temporary fix. Lee Townsend at UK says defeating the emerald ash borer will require some sort of biological control. Right now, entomologists are experimenting with a tiny, parasitic wasp. Townsend says they don’t sting people, but lay their eggs directly into emerald ash borer eggs and larvae.
“They search out their prey and attack them in a very focused way,” he said. “So that’s what we’re hoping for, getting pockets of these established that will multiply and spread on their own, and really have an impact.”
Some of these tiny wasps have been released in Jefferson County, with the hopes they’ll help stop the emerald ash borer before the county’s ash trees are decimated.
For information about the emerald ash borer, and how to protect your ash trees, click here.
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