Population Ecology Emergence, Seasonality, and Hybridization of Laricobius nigrinus (Coleoptera: Derodontidae), an Introduced Predator of Hemlock Woolly Adelgid (Hemiptera: Adelgidae), in the Tennessee Appalachians

Abstract From 2010 through 2013, adult emergence and seasonality of Laricobius nigrinus Fender, an introduced predatory species native to western North America, as well as hybridization with the native species Laricobius rubidus (LeConte), were evaluated using emergence traps and beat-sheet sampling in areas of previous release against hemlock woolly adelgid, Adelges tsugae Annand. The shortest emergence period of adult L. nigrinus was 7 wk beginning 22 October 2010, and the longest emergence was 15 wk beginning 17 October 2012. Native L. rubidus also were collected from emergence traps placed on the ground surface and beat-sheet samples all 3 yr, with emergence of L. rubidus initiating later than L. nigrinus each season. Seasonality of both Laricobius species was similar across a 44-mo study period. Adult L. nigrinus were present from October through April, and larvae of Laricobius spp. were collected from February to May. The average number of L. nigrinus from emergence traps was significantly greater than the average number of beetles collected from beat-sheet samples in 2010, while the converse was observed during 2012. Hybridization between L. nigrinus and L. rubidus was documented from 10.75% of specimens collected during 2010 and 2011, indicating periodic interbreeding between the introduced and native species. These findings suggest emergence trapping may be a useful method to assess establishment, population densities, and seasonality of Laricobius species in areas of release to enhance their use in management of A. tsuage

Discovery of Walnut Twig Beetle, Pityophthorus juglandis, Associated with Forested Black Walnut, Juglans nigra, in the Eastern U.S.

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

N2 Fixation of Common and Hairy Vetches when Intercropped into Switchgrass

Interest in sustainable alternatives to synthetic nitrogen (N) for switchgrass (Panicum virgatum L.) forage and bioenergy production, such as biological N2 fixation (BNF) via legume-intercropping, continues to increase. The objectives were to: (i) test physical and chemical scarification techniques (10 total) for common vetch (Vicia sativa L.); (ii) assess whether switchgrass yield is increased by BNF under optimum seed dormancy suppression methods; and (iii) determine BNF rates of common and hairy vetch (Vicia villosa L.) via the N-difference method. Results indicate that chemical scarification (sulfuric acid) and mechanical pretreatment (0.7 kg of pressure for one minute) improve common vetch germination by 60% and 50%, respectively, relative to controls. Under optimum scarification methods, BNF was 59.3 and 43.3 kg·N·ha−1 when seeded at 7 kg pure live seed ha−1 for common and hairy vetch, respectively. However, at this seeding rate, switchgrass yields were not affected by BNF (p > 0.05). Based on BNF rates and plant density estimates, seeding rates of 8 and 10 kg pure live seed (PLS) ha−1 for common and hairy vetch, respectively, would be required to obtain plant densities sufficient for BNF at the current recommended rate of 67 kg·N·ha−1 for switchgrass biomass production in the Southeastern U.S

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

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