Black Walnut Mortality in Colorado Caused by the Walnut Twig Beetle and Thousand Cankers Disease

Fig. 3. Cankers caused by Geosmithia are visible only after the outer bark is removed: (C) multiple cankers caused by Geosmithia developing on the trunk approximately 1 m from the ground.



Image from Plant Health Progress article:
Black Walnut Mortality in Colorado Caused by the Walnut Twig Beetle and Thousand Cankers Disease