Comparative flight responses of the walnut twig beetle, Pityophthorus juglandis, to varying release rates of ethanol in combination with aggregation pheromone in California and Tennessee

The walnut twig beetle (WTB), Pityophthorus juglandis, causes thousand cankers disease of walnut, Juglans sp., when phoretic Geosmithia morbida spores are introduced as WTB bores into the phloem. Thousand cankers disease has caused widespread mortality among native and adventive California black walnut, Juglans hindsii, as well as adventive eastern black walnut, J. nigra, in the western U.S.  Between 2010 and 2013 WTB was detected in Maryland, Ohio, Pennsylvania, Tennessee, and Virginia, presenting a threat to native J. nigra stands. In 2013, WTB was discovered in northern Italy.  Studies were undertaken in California and Tennessee to compare the flight response of WTB to different release rates of ethanol in combination with the commercially available aggregation pheromone lure as part of a program to optimize early detection methods for WTB. The release rates of ethanol ranged from 30 mg/d to 520 mg/d.