Thousand Cankers Coming? How to Spot Walnut Tree Killer

Jan 25, 2012

Thousand Cankers Coming? How to Spot Walnut Tree Killer

Fatal thousand cankers disease on a walnut tree: The illness is named for the many small lesions it causes on branches. For now it's not in Ohio. (Tennessee Department of Agriculture image.)

 COLUMBUS, Ohio -- Now you can get a free wallet-size ID card for spotting thousand cankers disease, which is a new, deadly walnut tree illness. It’s close to but not in Ohio yet.

And while state officials hope it never gets here, they want to find it quickly if it does. At risk: $1.2 billion -- the estimated value of lumber from Ohio’s black walnuts -- and tons of edible nuts.

By using the new card, “Landowners can help us find infestations early,” said Kathy Smith, forestry program director for Ohio State University Extension.

“Early detection hopefully means that an infestation would be found inhabiting a smaller area and would be easier to eradicate.”

OSU Extension co-produced the card with the Ohio Division of Forestry and Ohio Department of Agriculture as part of a new awareness campaign. Support came in part from the Renewable Resources Extension Act.

Single or multiple copies are free from OSU Extension’s Ohio Woodland Stewards Program, 210 Kottman Hall, 2021 Coffey Road, Columbus, OH 43210; 614-688-3421;

In the past 10 years, thousand cankers disease has caused widespread deaths of walnut trees in the western U.S., although scientists pegged it as the cause only recently, in 2008.

But now it’s been found to the east -- in Tennessee in 2010 and in Virginia and eastern Pennsylvania just last year.

The disease is caused by a fungus, Geosmithia morbida, which is spread by a bug called the walnut twig beetle. Both are thought to be native to parts of North America.

At first, infected trees show yellowing of the leaf canopy, small exit holes caused by the beetles, and many small lesions, or cankers, on the branches. All are shown on the card. The trees eventually die.

Only walnut trees -- especially black walnuts but also English, Arizona and California walnuts -- are affected.

Ohio landowners who suspect the disease should call the Ohio Department of Agriculture at 614-728-6400. The card includes that number as well.

A collaborative website on thousand cankers disease, produced by the international Walnut Council and parts of Purdue University and the U.S. Department of Agriculture, is at Included is a drop-down menu for updates on every state, including Ohio.

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