Thousand cankers disease: potential use of host kairomones for detection and monitoring of the insect vector, Pityophthorus juglandis.

Thousand cankers disease (TCD) has caused widespread death of black walnut trees throughout the West and was recently detected in Tennessee, Virginia and Pennsylvania. This disease complex is caused by a Geosmithia fungus vectored by the walnut twig beetle (WTB), Pityophthorus juglandis (Coleoptera: Curculionidae: Scolytinae).  Male WTB locate suitable black walnut hosts by orienting to host odors and, once on an appropriate tree, release volatile aggregation pheromones that coordinate mass attack and mating. No current technology exists to identify those trees that may be most susceptible to the beetle. In fact, monitoring and detection efforts for WTB rely on a pheromone lure that is effective from a distance of only ~20 m. Overall goals of this research are to develop a kairomone-based lure for WTB and determine the influence of genotypic variations and environmental stress on the relative resistance of black walnut to WTB attack. In this project, we tested the bioactivity of volatiles released from nine different cultivars of black walnut and found significant variation in their attractivity to adult beetles. Understanding those factors that influence the susceptibility of black walnut to colonization by P. juglandis and infection is essential for managing this disease complex and determining its potential economic and ecological impacts.