The fungus causing Thousand Cankers Disease in walnut trees has been detected for the first time in Indiana. The discovery of the fungus, Geosmithia morbida, was on small weevils of the Stenomimus pallidus family when they emerged from two stressed trees. The discovery site was in a black walnut plantation in Yellowwood State Forest in Brown County. It was also the first time the fungus was detected on an insect other than the walnut twig beetle.
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. Neither this survey nor any other previous surveys have detected the walnut twig beetle in Indiana.
Originally found in New Mexico, 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 are also common in the state’s urban and rural forests.
The documentation in Indiana adds the Hoosier State to 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 quarantine only restricts movement of black walnut out of the plantation. Movement of black walnut from other areas of Brown County is not restricted.
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 trees in the plantation do not currently show symptoms of the disease, according to Marshall. Should the disease status in the plantation change, the trees can be cut and destroyed to prevent spread out of the plantation.