"Black leg" - a disease of stem cuttings. Particularly susceptible pelargonium. The base of the cutting of the defeat of the fungus blackens and rots. Contributes to this wetland soils with poor aeration of the earth. Control measures. With a large lesion of cutting it destroyed. If you hit a small part, it is removed, slice sprinkled with powdered charcoal or gray and put in fresh looser soil. Ensure that the soil has been moistened.