To prevent pests and diseases, practice good hygiene by removing fallen leaves and debris. Use insecticidal soap or neem oil to control pests. For diseases, improve air circulation and avoid overhead watering. Applying fungicides when necessary can also help. Regularly monitor your Plumeria garden to maintain its health.

Cut away the rotting portion until only healthy tissue remains. Let the cut area dry and then replant in fresh, well-draining soil.