Walnut Twig Beetle (image) USDA Forest Service - Pacific Southwest Research Station Share Print E-Mail Caption The walnut twig beetle excavates under bark and inoculates the tree with the Geosmithia morbida fungus, resulting in Thousand Cankers Disease. Credit Photo by Curtis Utley, CSUE, Bugwood.org. Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.