Soil-borne diseases are managed by improving organic matter and biological activity. Cultural, biological, and physical methods such as rotation, sanitation, pruning, and selection of disease resistant varieties are all part of organic disease management. Some natural substances, such as clays, and a few synthetic fungicides such as copper sulfate are permitted by the USDA National Organic Program Standards when used in conjunction with the farm plan and used according to the restrictions found on the National List.