The plants have a fungus called Botrytis cinerea. It attacks stems, buds and leaves. This disease is most common in cloudy, rainy weather. Remove diseased buds. Fungicides prevent disease but do not cure this fungus. Fungicides like basic copper sulfate or Mancozeb are of limited effectiveness against this disease this season. In the fall, cut any diseased plants back to the ground or just below the ground and dispose of the infected material. Add well-composted organic material as a light mulch in early fall to help add nutrients and improve the soil.