State hopes to stop introduction of potentially devastating Thousand Cankers Disease

May 27 , 2010

LANSING-Michigan Department of Agriculture (MDA) Director Don Koivisto today announced the implementation of an exterior state quarantine against Thousand Cankers Disease (TCD) to protect Michigan’s black walnut industry from this disease that is currently devastating walnut trees in the western U.S.

Originally found to be killing trees in Colorado as early as 2003, TCD was only recognized as a disease in 2008. TCD primarily affects black walnut and is caused by a fungus transmitted to the tree by the walnut twig beetle. Thousand Cankers Disease has produced widespread death of black walnut in many western states during the past decade. But, other species of walnut such as Arizona walnut, English walnut, and California walnut have all shown varying degrees of susceptibility to this fungus.

The fungus is carried into the tree when the walnut twig beetle tunnels into the tree and wounds it. This disease is transmitted much like how Dutch elm disease is spread by the elm bark beetles. Branches and trunk tissue are killed by repeated infections of the fungus as the beetles carry it to new bark tissue creating an infectious cycle, which is why it’s called Thousand Cankers Disease. Long range spread occurs when infested trees and parts of trees such as logs, green lumber or firewood are transported by people to other parts of the country.

"MDA wants to prevent the introduction of this new invasive to preserve the state’s walnut resource. Our walnut industry would suffer huge losses if Thousand Canker Disease were to be brought into the state," said Koivisto. “Michigan has an estimated 8.5 million black walnut trees, whose sawtimber value is estimated at $86 million. Black walnut is one of the most desirable woods used in the furniture industry and is sought after by customers world-wide.”

MDA’s exterior state quarantine places restrictions on the movement of black walnut logs, green lumber, and nursery stock from the current quarantined states of Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, Washington, and Utah. In addition, Michigan’s quarantine regulates shipment of hardwood firewood from those states with the only exemptions being nuts and nut meats as well as kiln dried walnut wood.

"Regulating the movement of walnut logs and other timber products is essential to the continued health and well-being of black walnut in Michigan," said Koivisto. "We need the help of every homeowner, sawmill, and log broker to make sure this disease never enters Michigan."

When looking for TCD, pay attention to declining trees as early symptoms include yellowing and thinning followed by death in two to three years. A tree with dead leaves ishighly suspect and is considered to be a more advanced symptom. Branches collapse in the late spring and summer with the dead leaves remaining attached to the branch.

Individuals or businesses found violating the state’s Thousand Cankers Disease of Walnut Quarantine are subject to fines ranging from $1,000 to $250,000 and jail time of up to five years.

Additional information about Thousand Cankers Disease of Walnut is available on the MDA website at www.michigan.gov/mda or at http://www.thousandcankerdisease.com/.

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