Indiana property owners should monitor walnut trees for symptoms of thousand cankers disease, says Purdue University forestry expert, after disease is detected in southwest Ohio

Wendy Lisney

WEST LAFAYETTE, Indiana , September 4, 2013 (press release) – Discovery of the deadly thousand cankers disease in walnut trees in a southwest Ohio county should prompt Indiana residents to be on the lookout for symptoms in their walnut trees, a Purdue University Forestry and Natural Resource specialist says.

No cases of the tree disease have been reported in Indiana, but property owners should be vigilant for signs of it, said Elizabeth Jackson, executive director of the National Walnut Council and the Indiana Forestry and Woodland Owners Association, both based at Purdue.

"Residents need to know that thousand cankers disease has not been found in natural areas yet, but almost every incident has been in an urban, industrial or an area outside the suburbs," Jackson said. "Healthy trees are less affected, so keeping your trees healthy and vigorous will help reduce the risk of TCD."

Thousand cankers disease, which has no known treatment yet, is a result of a walnut twig beetle carrying the fungus Geosmitha morbida. Adult beetles tunnel into the tree just beneath the outer bark and cause cankers - areas of dead plant tissue - that can block water and nutrient transport throughout the tree. The disease had been confirmed in several western states during the last 10 years and in recent years was spotted in Tennessee, Pennsylvania and Virginia.

The Ohio Department of Agriculture has confirmed thousand cankers disease in walnut trees in Butler County north of Cincinnati adjacent to Indiana's Dearborn County. The affected trees are in an area 15-25 miles east of the Indiana border.

Jackson said firewood and other types of untreated wood should not be transported. Many insect infestations, including some involving TCD outbreaks, result from infested wood being moved into an uninfested area.

"There are very stringent requirements on firewood now," Jackson said.

Symptoms of TCD commonly include thinning crowns, yellowing or wilted leaves in the crown and limbs that died recently. But Jackson said leaves turning yellowish in August and September and falling off the tree are not necessarily symptoms of TCD. They can be symptoms of anthracnose, an unrelated disease, or drought stress. The leaves of a tree infected by TCD will wilt but stay attached to the tree.

Tree owners observing a black walnut tree with yellow leaves on the outer branch in the tree crown through September can file a report through the Forest Pest Outreach Survey on the Indiana Department of Natural Resources website at www.in.gov/dnr/entomolo/7416.htm. They also can print the form and send it by fax or email, or call 866-663-9684.

The Hardwood Tree Improvement and Regeneration Center at Purdue is determining if clones produced in Purdue's breeding program for black walnut have any differences in tolerance to the walnut twig beetle, which carries the TCD fungus.

"We are determining if wild trees in the forest have any difference in their resistance," said Charles Michler, project leader at the center. "The disease could have come from numerous places in the western United States, and we are trying to pinpoint where it came from. All of this information will help us if we need to deploy resistant trees in the future."

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