The emergency rule, issued by the DNR Division of Entomology and Plant Pathology, became effective August 30 and will help protect Indiana’s black walnut trees from the disease.
The rule applies to walnut products from Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, Tennessee, Utah, and Washington.
Banned products originating from or traveling through the affected states include walnut nursery stock, unprocessed walnut lumber, or any other walnut material, such as logs, stumps, roots, branches, mulch, wood chips, other products created from walnut trees, and hardwood firewood.
Products exempt from the rule include nuts, nut meats, hulls, kiln-dried lumber with squared sides and no bark, and finished products such as furniture, instruments, and gun stocks.
Indiana joins Kansas, Michigan, Missouri and Nebraska in banning the transport of walnut products from the infested states.
Although TCD has not been found in Indiana, it is a major threat to the state’s black walnut resource. Black walnut is the most valuable tree in Indiana based on the dollar value of wood produced, mainly walnut veneer, as well as timber and nuts.
There are an estimated 31.5 million walnut trees in Indiana. Approximately 17.7 million board feet of black walnut is harvested annually with a value of $21.4 million. If all forest walnuts in Indiana were lost because of TCD, it would represent a $1.7 billion loss. State Forester John Seifert, director of the DNR Division of Forestry, said the estimates do not include the value of urban trees and investments landowners have made for black walnut plantations and tree improvement over the past 30 years.
“We have much to lose from the spread of TCD,” said Phil Marshall, state entomologist and director of the DNR Division of Entomology and Plant Pathology. “It is crucial that we avoid its introduction into Indiana. This rule essentially protects our state, allowing us to prevent potentially infected material from entering Indiana.”
Forest landowners do not need to harvest or cut their black walnut trees as a result of the disease or the emergency rule. If you notice a suspicious decline in black walnut trees or otherwise suspect an infestation of TCD, call 1-866-663-9684 (1-866-NO EXOTIC). If approached by individuals offering to cut a black walnut because of the disease, contact the DNR or a consulting forester to have the tree checked for disease.
Originally found in Arizona, TCD affects many types of walnut trees to varying degrees but is lethal to black walnuts, which often are grown in plantations in Indiana but also are common in the state’s urban and rural forests.
TCD is spread by walnut twig beetles carrying a newly identified fungus. Smaller than a pinhead, the beetles bore into walnut branches, feeding on the tree’s tissues and depositing the fungus that creates a canker, or dead area, under the bark. Multiple feedings cause the formation of thousands of cankers under the bark and destroys the tree’s ability to transport water and nutrients. Gradually, branches die, and then the entire tree.
Walnut trees affected by the disease typically die within two to three years after symptoms are noticed.
“It is amazing that this much destruction could come from such a tiny beetle,” Marshall said. “The walnut twig beetle is just the latest invasive pest to threaten Indiana’s forests and our $8 billion timber industry. Indiana already has issues with the gypsy moth and emerald ash borer. It’s fairly simple. To preserve our forests, people must not bring destructive insects and diseases into Indiana, and we need to do our best to inform the public and take management steps to protect our forests.”
More information on TCD can be found at www.dnr.IN.gov/entomolo or at www.ppdl.purdue.edu/PPDL/current_interest.html#WTCD. The timber industry businesses needing assistance with this rule need to contact the Division of Entomology and Plant Pathology at (317) 232-4120.