By CELESTE BAUMGARTNER
COLUMBUS, Ohio — Look at the word “LIBERTY” on a dime. The walnut twig beetle, which is about the size of the “I” in that word, is causing some big headaches for foresters in Ohio, Tennessee and other states.
That beetle carries a fungus that causes thousand cankers disease (TCD) and it can kill Eastern black walnut trees. The Ohio Department of Agriculture (ODA) announced the first discovery of walnut twig beetles in traps they set at a wood processing plant in Butler County, said Dan Kenny, acting assistant chief of the Division of Plant Health.
No trees have been infested with TCD in Ohio – so far. But they have been found in Tennessee. The Tennessee Department of Agriculture (TDA) discovered the disease in Knoxville in 2010. That was the first detection east of the Mississippi River, said Tim Phelps, Tennessee Division of Forestry.
Several counties in eastern Tennessee have been quarantined to help in preventing the spread of the beetle.
The disease was first found in Colorado in 2003 and has since been detected in 11 other states, Kenny said. In September 2012, ODA enacted an exterior state quarantine regulating the transportation of walnut products from areas of the 12 affected states.
The University of Colorado discovered the relationship between the walnut twig beetle and TCD, Phelps said. Unlike other problem species such as the Asian longhorned beetle and emerald ash borer, which came from foreign countries, this little critter is native to the southwestern United States.
Also, the disease is called “thousand cankers” because it takes a large number of beetles to spread the disease around before the tree dies, he explained. The population of beetles takes many years to build up in a tree. The infestation in Knoxville probably began about a decade before it was found.
“There is a lot to learn about this still, biologically, just in how it acts,” Phelps said. “Does it affect urban trees more than rural trees? So far we haven’t found it in the woods, we’ve only found it in urban environments. Maybe there’s a relationship there, where the Eastern black walnut trees are already under a little stress and they’re dying faster because of that.”
Across all of its native range the Eastern black walnut is a valuable tree for its beautiful, fine-grained wood and for its ecological value, he said. It provides food for wildlife and does well in environments with a lot of water or near streams, where it holds soil banks in check.
“Walnut is a high-value species, so this is definitely something of concern,” Kenny added. “Ohio ranks second or third in (numbers of) standing walnut trees; that is why we wanted to determine if the disease was here or not. There is no known effective treatment at this time.”
Both Phelps and Kenny advise landowners to be cautious moving firewood because of the walnut twig beetle, as well as other problem species. Landowners should watch for signs of TCD on their walnut trees. If they suspect they could be infested, in Ohio they should contact the local forester, extension office or ODA at 614-728-6201.
In Tennessee concerned landowners can go through www.tn.gov/agriculture/tcd for an online symptoms checklist and a report form, or call TDA’s Regulatory Services Division at 800-628-2631.