Thousand Cankers Disease Complex: A Forest Health Issue that Threatens Juglans Species across the U.S.

摘要

Thousand Cankers Disease (TCD) is a disease complex wherein the fungus ( Geosmithia morbida ) is vectored by the walnut twig beetle (WTB, Pityophthorus juglandis ). The disease causes mortality primarily of eastern black walnut ( Juglans nigra ), although other walnut and wingnut ( Pterocarya ) species are also susceptible. Black walnut is native to the Eastern and Midwestern U.S. but is widely planted in western states. Total standing volume in both urban and forested settings is approximately 96 million cubic meters, and is valued at $539 billion. Although native to the Southwestern U.S., the range of WTB has expanded considerably. The spread of G. morbida coincides with that of WTB. TCD was introduced into Tennessee in 2010, and has spread to seven eastern states. Trees infected with TCD exhibit drought-like symptoms, making field detection difficult without molecular and/or morphological methods. The recently sequenced G. morbida genome will provide valuable research tools focused on understanding gene interactions between organisms involved in TCD and mechanisms of pathogenicity. With no chemical treatments available, quarantine and sanitation are preeminent options for slowing the spread of TCD, although biological control agents have been discovered. High levels of black walnut mortality due to TCD will have far-reaching implications for both eastern and western states.