The causative agent of mosaic disease in potato is a virus. This disease is caused by several types of viruses, including potato virus Y, potato leaf roll virus, and others. These viruses lead to characteristic symptoms in potato plants, such as mottled or mosaic patterns on the leaves, stunted growth, and reduced tuber quality and yield. The viruses are transmitted through infected plant material, aphids, or mechanical means. Management of mosaic disease involves using virus-free seed potatoes, controlling aphid populations, and removing infected plants to prevent the spread of the viruses. By implementing these practices, farmers can reduce the impact of mosaic disease on potato crops.