The disease overwinters on fallen diseased leaves so dispose of infected leaves in the fall. A large number of fungi cause leaf spots on hickory. Severe infections can cause defoliation. Many of the fungi overwinter on diseased leaves, dispose of infected leaves when they fall. Witches broom can follow a leaf spot disease caused by Microstroma juglandis.
Symptoms are yellow blotches on the upper sides of the leaves but white on the undersides.
Severe infections may cause defoliation and when the fungus invades the stem a witches broom forms. Leaves on the stems of the witches broom are yellowish, small, and fall prematurely. Prune out witches brooms when they form. Powdery mildew causes a white powdery growth on the leaves. If the disease occurs late in the season, no chemical control will be needed.