Abstract
Thousand cankers disease (TCD) is an insect-mediated disease of walnut trees (Juglans spp.) involving walnut twig beetle (Pityophthorus juglandis) and a fungal pathogen (Geosmithia morbida). Although first documented on walnut species in the western U.S., TCD is now found on black walnut (J. nigra) in five states in the eastern U.S. Most collections of P. juglandis or G. morbida are from trees in agriculturally- or residentially-developed landscapes. In 2013, 16 pheromone-baited funnel traps were deployed in or near black walnuts in forested conditions to assess the risk of infestation of forested trees by P. juglandis. Four of the 16 funnel traps collected adult P. juglandis from three forested areas (one in North Carolina and two in Tennessee). These collections, while in forested settings, may still be strongly influenced by human activities. The greatest number of P. juglandis (n = 338) was collected from a forested location in an urbanized area near a known TCD-positive tree. The other two forested locations where P. juglandis (n = 3) was collected were in areas where camping is common, and infested firewood may have introduced P. juglandis unintentionally into the area. Future studies to assess P. juglandis on more isolated forested walnuts are planned.
Highlights
Black walnut, Juglans nigra, is native to the eastern and midwestern U.S, where it is widely distributed across a variety of sites from open fields to forests [1]
In July 2010, Thousand cankers disease (TCD) was documented for the first time in the native range of black walnut in the eastern U.S in Tennessee. Both P. juglandis and G. morbida were confirmed from black walnut trees in Knoxville, Knox County, Tennessee [7,8] (Figure 1)
While G. morbida-infected trees were documented on the forest edges at two locations in the Great Smoky Mountains National Park (GRSM) (Big Creek and Cataloochee Cove; Figure 1) [11], no P. juglandis was confirmed from black walnut at any sampled location
Summary
Juglans nigra, is native to the eastern and midwestern U.S, where it is widely distributed across a variety of sites from open fields to forests [1]. Both P. juglandis and G. morbida were confirmed from black walnut trees in Knoxville, Knox County, Tennessee [7,8] (Figure 1).
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