Initial Assessment of Thousand Cankers Disease on Black Walnut, Juglans nigra, in Eastern Tennessee

Abstract

In 2010, thousand cankers disease (TCD) was documented in Tennessee, representing the first confirmation of this disease in the native range of black walnut and the first known incidence of TCD east of Colorado. Tennessee Department of Agriculture personnel conducted surveys to determine the extent of TCD in counties in eastern Tennessee. Samples of symptomatic black walnuts were sent to the University of Tennessee for processing. The causative agents, walnut twig beetle, Pityophthorus juglandis, and the fungal pathogen Geosmithia morbida, were documented on the same trees in four counties. Tree mortality was observed in two counties, and tree decline was observed in at least 10 counties although it may be attributed to previous droughts or to TCD. In 2010, four confirmed counties were quarantined by TDA, and 10 buffer counties were also regulated. Research is underway to further assess the incidence and impact of TCD on black walnut in Tennessee.

Keywords

• distribution
• forest threat
• Geosmithia morbida
• insect/fungal interactions
• native range
• Pityophthorus juglandis
• walnut twig beetle