Sanitation measures to control walnut twig beetle (Pityophthorus juglandis) emergence from felled black walnut logs

The walnut twig beetle, Pityophthorus juglandis (Blackman) and its fungal associate Geosmithia morbida have recently been discovered to produce thousand cankers disease.  The disease occurs in multiple walnut species, but it has devastated black walnut (Juglans nigra) populations in several western states.  Pityophthorus juglandis is native to the southwestern United States, but its geographic range is expanding, as is incidence of thousand cankers.  Finding effective management options for the disease is critical to decrease further expansion into urban and eastern walnut forests.  In a series of experiments, we tested the effect of chipping, insecticides, and temperature treatments to control the beetle.  Chipping infested material was over 90 percent effective, and emergence from chipped material ceased within five weeks.  Insecticidal treatments were more than 80 percent effective.  Heat treatments of 60°C for 30 minutes were effective phytosanitary methods to control P. juglandis, while cold treatments of -25°C for seven days were over 99 percent effective.  Although several temperature treatments eliminated P. juglandis populations, re-colonization occurred if logs were exposed to beetles.  These experiments provide baseline management options for walnut logs infested with P. juglandis, and show the importance of properly storing treated logs to prevent re-colonization.