Description
    Walnut anthracnose is the most common leaf spot disease of black walnut and occurs wherever black walnut is grown.

    The fungus causes small dark brown to black circular spots up to 1/2 inch in diameter on the leaves. These spots are usually bordered with yellow. Wet spring weather is ideal for the development of the disease, although symptoms may not become visible until June or July.

Injury
    By mid-August leaves on trees infected with walnut anthracnose begin to turn yellow and drop. The growth rate of mildly to heavily infected trees is reduced. Heavily infected trees may be completely defoliated. Trees are not killed by the disease unless they are under stress from other causes. Anthracnose may also affect the quality of the nuts.
Control
    Contact your service forester or county extension agent for recommended control. Fertilization with nitrogen may help reduce the harmful effects of this disease.