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

Fig. 1. Symptoms of thousand cankers disease in Juglans nigra: (A) Yellowing of leaves and branch dieback during early stages of disease. Note that the bark on branches and trunk remains firmly attached even in final stages of disease and there is no external evidence of cankers.



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