Beetles that destroy ash trees reach Tennessee

By Morgan Simmons
Knoxville News Sentinel
Thursday, July 29, 2010

A small, metallic-green beetle that destroys ash trees has made its way to Tennessee.

For the past several years, state agriculture officials have been on the lookout for the emerald ash borer, an exotic insect pest discovered in southeastern Michigan in 2002 that has since spread to 14 U.S. states and two Canadian provinces.

Tennessee's first outbreak was discovered near Knoxville two weeks ago. An out-of-state forestry professional happened to notice an ash tree with tell-tale signs of emerald ash borer damage at a truck stop in Knox County near the Loudon County line. Last week, the U.S. Department of Agriculture positively identified an adult beetle collected at the site as an emerald ash borer.

In response to the find, the Tennessee Department of Agriculture will issue a quarantine in Knox and Loudon counties prohibiting the movement of firewood, ash nursery stock, ash timber and other materials that can spread the emerald ash borer.

"A lot of states have tried to eradicate it, and none have been successful," said Gray Haun, plant certification administrator for the Tennessee Department of Agriculture. "The best we can hope for is to contain the infestation and slow the spread with some sort of biological controls."

A native of Asia, the emerald ash borer kills all four native species of ash - green, white, blue and black. The adults lay their eggs on the tree, and after hatching, the larvae feed beneath the bark, inscribing tunnels that kill the tree in about three years by disrupting the flow of nutrients and fluids.

Ash wood is commonly used in hardwood flooring, tool handles, kitchen cabinets and baseball bats. According to a 2009 report by the USDA, the emerald ash borer's impact on urban areas could mean the loss of up to 90 million trees and up to $60 billion in landscaping damages.

Tennessee agricultural officials estimate that 10 million urban ash trees across the state are potentially at risk.
In the coming weeks, plant inspectors and foresters with the Tennessee Department of Agriculture, the USDA, and the Tennessee Valley Authority will set up a command center in Knoxville to survey trees in order to assess the extent of the infestation.

Because firewood is a common medium for the movement of emerald ash borers, officials are urging area residents to not transport firewood - even within Tennessee - and not to buy or move firewood from outside the state.

In anticipation of the emerald ash borer spread, the Great Smoky Mountains National Park already has set up insect traps and imposed restrictions at campgrounds that require all firewood brought in from quarantined states to be burned.

Ash trees in the Smokies typically are found in cove hardwood forests at low to mid-elevations. The park contains two species of ash, green and white, both of which produce large numbers of seeds that feed birds and mammals.

Kristine Johnson, supervisory forester for the Smokies, said the inevitable loss of ash trees will be another blow to the park's ecosystem that already has suffered from other exotic pests and diseases that have wiped out hemlocks and beech trees.

Of the recent emerald ash borer discovery near Knoxville, Johnson said she was "sad, but not surprised" by the news.

"We're sorry to learn that yet another important tree species is likely to be lost," Johnson said.

Morgan Simmons may be reached at 865-342-6321.

© 2010 Scripps News Service - Online