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Thousand Cankers Disease Discovered in East Tennessee

Just one week after the first signs of Emerald Ash Borer beetle in Tennessee were found, the Tennessee Department of Agriculture (TDA) confirmed a state forester’s discovery of Thousand Cankers Disease (TCD) in the same area – Knox County in East Tennessee.  Thousand Cankers Disease is a fungus that affects walnut trees and is potentially devastating to the walnut lumber industry and threatens urban landscapes.  TDA estimates there are 26 million black walnut trees on Tennessee public and private timberland potentially valued as high as $1.47 billion.  An approximately 1.38 million walnut trees in urban areas throughout Tennessee are threatened as well.

Until July 2010, the disease was only known to occur in western United States where over the past decade it has been involved in several large scale die-offs of walnut, particularly black walnut, Juglans nigra.  The disease’s confirmation in Knox County is one of the first outbreaks identified east of the Mississippi River.  This find also ends speculation on the source of the disease’s spread — human transport of walnut twig beetle-containing walnut wood probably occurring a decade or more ago. Walnut wood is extremely infectious (i.e., contains fungus bearing bark beetles) for at least 2-3 years after trees are cut.  The beetles are capable of surviving on small pieces of wood, as long as some bark is attached, and some beetles can even survive normal wood chipping.

New infestations from thousand cankers can become established with the movement of a single piece of wood. As the disease develops slowly, and external symptoms may not become visible for 10-20 years after the original establishment, it is possible that additional, undetected infestations are present in the eastern US.

TCD is a progressive disease that kills a tree within two to three years after initial infection. The disease-causing fungus, Geosmithia, is transmitted by a small twig beetle.  Branches and trunk tissue are killed by repeated infections by the fungus, as the beetles carry the fungus into new bark.

Citizens are urged to work with TDA to prevent the spread of both the beetle and the fungus it carries.  The TDA plans to issue a quarantine in Knox county prohibiting the movement of firewood and black walnut nursery stock and limiting the movement of  black walnut timberland other material that can spread TCD. TDA plant inspectors and foresters will conduct a thorough survey of trees in the areas to assess the extent of the infestation and to see if more quarantines are warranted.

What can you do to help stop the spread of this disease and the Emerald Ash Borer beetle?  TDA officials offer the following guidelines:

  • Don’t transport firewood, even within Tennessee. Don’t bring firewood along for camping trips. Buy the wood you need from a local source. Don’t bring wood home with you.
  • Don’t buy or move firewood from outside the state. If someone comes to your door selling firewood, ask them about the source, and don’t buy wood from outside the state.
  • Watch for signs of infestation in your black walnut trees. If you suspect your black walnut tree could be infested with TCD, visit www.TN.gov/agriculture/tcd for an online symptoms checklist and report form or call TDA’s Regulatory Services Division at 1-800-628-2631.

For more information about other programs and services of the Tennessee Department of Agriculture visit www.tn.gov/agriculture.

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