Septoria is a genus of fungi that includes many species responsible for plant diseases. Some species, such as Septoria apiicola, S. oxyspora, and S. nodorum, cause diseases of celery, tomatoes, and cereals including wheat, rye, and barley. These leaf-spot diseases cut yields and grain quality, threatening raw-material supply for the food industry. Growers manage them with resistant varieties, rotation, and fungicides. Healthy crops mean secure food supplies. Plant pathologists work to stay ahead of them. Vigilance protects harvests and food supplies.