Extensive leaf spotting causes yellowing, curling, and premature defoliation and lesions appear may also appear on the nut husks as dark sunken spots. These affected nuts may have reduced meat quality and may drop prematurely. In most cases, control of anthracnose is unnecessary because the disease is usually not damaging to the long-term health of trees. When control is desired, various techniques can help reduce the severity of the disease. Raking and destroying fallen leaves and twigs and pruning out dead branches on the tree will help reduce the overwintering population of anthracnose fungi and pruning will also increase air circulation in the canopy, thereby reducing the time that wet conditions, which favor fungal infection, are present on leaf surfaces.
Healthy trees are more likely to recover from a severe anthracnose attack than are stressed trees.
Mulching and watering during dry periods will help keep trees healthy. Chemical sprays to control anthracnose are rarely justified except when the disease occurs in stressed or recently transplanted trees, or when the disease causes repeated defoliations. For walnut anthracnose, the first application should be made when the leaves begin to unfold, followed by additional weekly sprays as needed, especially if rainy weather persists. Read label directions for more information on timing and application.