Black spots occur on young nuts and shoots. Nearly ripe nuts have large black spots on the husks. Infected nuts fall prematurely or may have husks, shells, and kernels blackened and ruined. Copper fungicides may control this disease. First sprays must be applied in early prebloom.
Powdery mildew causes a white coating on the leaves.
Chemical controls should not be necessary. If needed use benomyl. During periods of high temperature and drying winds, walnuts will scorch. Make sure plants have adequate soil moisture. Visuals associated with this text.