(BROWN CO.) - The fungus that causes Thousand Cankers Disease (TCD) in walnut trees has been detected for the first time in Indiana.
The Indiana Department of Natural Resources says the discovery of the fungus, Geosmithia morbida, occurred on small weevils that emerged from two stressed trees in a black walnut plantation in Yellowwood State Forest in Brown County. The DNR says this also marked another first, in that it was the first time the fungus was detected on an insect other than the walnut twig beetle.
The DNR says the fungus was discovered as a result of a survey for insect pests and fungi in Indiana and Missouri. The U.S. Forest Service-led survey was a cooperative effort with scientists at the University of Missouri and Purdue University. The survey did not detect the fungus, walnut twig beetle or the weevil in Missouri.
Originally found in New Mexico, DNR officials say TCD affects many types of walnut trees to varying degrees. However, the disease is lethal to black walnuts, which often are grown in plantations in Indiana and are also common in the state's urban and rural forests.
Indiana joins Maryland, North Carolina, Ohio, Pennsylvania Tennessee, Virginia and eight western states with the disease.
State Entomologist Phil Marshall, director of DNR Division of Entomology & Plant Pathology, has ordered the plantation quarantined.
The DNR Division of Entomology & Plant Pathology, DNR Division of Forestry, U.S. Forest Service and Purdue University are conducting additional studies in the plantation to better understand the disease and insects there.
The quarantine only restricts movement of black walnut out of the plantation. Movement of black walnut from other areas of Brown County is not restricted.
"We have much to lose from the spread of TCD," Marshall said. "It is important that we repeat the study to understand the role of the weevil and occurrence of the fungus in the trees."
He says that walnut twig beetles that typically carry the fungus are smaller than a pinhead. They 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 eventually dies.
The DNR says this detection does not change or eliminate the current TCD quarantine that restricts movement of walnut into Indiana from other infested states. Indiana sawmills, veneer mills and log buyers must still comply with Indiana's TCD quarantine before they bring walnut from infested states into their location. The department adds that forest landowners do not need to harvest their black walnut trees as a result of this detection.
If you notice a suspicious decline in black walnut trees or otherwise suspect an infestation of TCD, call the DNR at 1-866-663-9684. If approached by someone offering to remove black walnut trees because of the disease, notify the DNR or a consulting forester to have the tree checked.
More information on TCD visit dnr.IN.gov/entomolo/6249.htm.
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