TCD results from the combined activity of Geosmithia morbida
fungus and the walnut twig beetle (WTB, Pityophthorus
juglandis). The WTB has expanded both its geographical and host
range over the past two decades, and, coupled with Geosmithia
morbida, walnut mortality has occurred in California, Oregon,
Washington, Idaho, Utah, Arizona, New Mexico, and Colorado. In
July 2010, TCD was first reported east of the 100th meridian in
Knoxville, Tennessee. This raised concerns that large native
populations of black walnut in the eastern United States may
suffer severe decline and mortality. Therefore, surveys were
conducted in various states in 2011, and TCD was found in
Pennsylvania and Virginia. Black walnut is a significant
economic, social and environmental resource, and appears to be
highly susceptible to TCD. Black walnuts exhibit little to no
resistance to the pathogen and its vector. News and Information
There is no federal regulation in place for TCD; however,
several states have set up exterior quarantines.