Friday, February 25, 2011

Minnesota Department of Agriculture implements exterior quarantine to protect state’s walnut trees from deadly disease

Michael Schommer, Communications Director

Quarantine prevents import of walnut trees and wood from states infested with Thousand Cankers Disease

ST. PAUL, Minn. – Minnesota Agriculture Commissioner Dave Frederickson this week moved to protect the state’s 6 million eastern black walnut trees and the state’s walnut timber producers by issuing a temporary exterior quarantine restricting the import of walnut trees and certain related products into Minnesota from areas known to be infested with Thousand Cankers Disease (TCD).

TCD is caused by a fungus carried by a tree pest called the walnut twig beetle.  The beetle attacks the walnut tree, introducing the fungus while it tunnels under the bark.  This results in small cankers, or dead areas, under the bark.  As more beetles attack the tree, these cankers grow together and cut off the tree’s circulation.  This ultimately kills the tree.  To date, TCD has been found in Arizona, California, Colorado, Idaho, New Mexico, Oregon, Tennessee, Washington, and Utah.  The MDA quarantine restricts movement of products potentially harboring TCD from those states and from other potentially infested areas into Minnesota.

The list of walnut products covered by the quarantine includes live walnut trees, walnut logs, walnut lumber, walnut firewood, walnut nursery stock, wood chips and mulch made from walnut wood, walnut branches and roots, and packaging materials made from walnut wood.  The quarantine does not apply to walnut nuts, nutmeat, walnut hulls, finished products made from walnut wood without bark, or processed lumber that is 100 percent bark-free, and kiln-dried with square edges.

“By taking this action, we will help protect a valuable part of our economy and our environment from needless damage,” Commissioner Frederickson said.  “This targeted quarantine will help prevent the loss of millions of trees and avoid damage to a valuable segment of our state’s forestry industry.”

The black walnut tree is an important tree for Minnesota’s environment and economy.  The tree is a natural part of the southeastern Minnesota landscape, and it is highly valued for its wood.  Every year, Minnesota harvests up to 2 million board feet of black walnut for use in products such as furniture and musical instruments.

MDA has the statutory authority to issue quarantines excluding harmful plant pests.  The TCD quarantine was implemented with input from the Minnesota Department of Natural Resources and the U.S. Forest Service.  MDA will seek public comment prior to replacing this temporary quarantine with a formal quarantine.  That formal quarantine may contain additional or different conditions based on information offered by the public.  More information about TCD and the quarantine can be found on MDA’s website at 


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