Place the plant in a dry, ventilated room and withold water until progress of the disease is halted. You may need to remove the damaged portions, rerooting the top part if necessary. Cacti and succulents are particularly susceptible to stem and root rot. They should always be kept fairly dry, particularly during winter months. This fungal disease can develop on any above-ground part of the plant as a result of high humidity or overcrowding, or if dead leaves or blossoms have been left on the plant.
Symptoms vary from plant to plant but the disease generally appears as a fuzzy grey growth.
Remove old leaves and flowers, increase ventilation and keep in drier conditions. Treatment with a recommended fungicide may be necessary. Infection only occurs under moist air conditions or if standing water is left on the foliage for prolonged periods. Affected plants collapse and die. Damping off fungi also cause seed decay.