There are 3 possible causes of death for your Elephant Bush: Overwatering, underwatering, and pest infestation. 1.   Overwatering If the leaves of the Portulacaria afra are turning yellow, its roots could be starting to rot due to overwatering. Another symptom of overwatering is the succulent’s leaves falling. Cut out any part of the plant that shows deterioration or infection. If left unattended, the infected area could spread and contaminate the entire plant. 2.   Underwatering The leaves of Portulacaria afra can dry up and shrivel and eventually, fall off if it does not receive enough water.  Perform frequent checks on the dryness of the soil. Check if the top layer of the soil is dry to the touch before giving the plant water.  3.   Pest Infestation Portulacaria afra attracts mealybugs, spider mites, and whiteflies. Brush off the mealybugs from the leaves by wiping them with a cotton ball dipped in denatured alcohol. A mild insecticide may get rid of the spider mites and whiteflies. If Elephant Bush is located in a garden with other succulents, transfer the pot to another location to prevent the pests from transferring to the rest of your plants.