WEST LAFAYETTE, Ind. — 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 said.
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 to 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
“There are very stringent requirements on firewood now,”
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.”