Canker in Black Walnut Tree (IMAGE) Purdue University Caption This is a canker on an eastern black walnut tree. The beetle that carries the fungus causing thousand cankers disease is visible in the canker's upper left corner. Credit (Colorado State University photo/Ned Tisserat) Usage Restrictions Credit: (Colorado State University photo/Ned Tisserat) License Licensed content 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.