To protect Plumeria from pests naturally, introduce beneficial insects like ladybugs or lacewings, which can prey on common pests like aphids and mealybugs. Companion planting with herbs like basil or marigolds can deter certain pests. Spraying neem oil or horticultural oils can help control pests without harming beneficial insects. Regularly inspect your Plumeria for signs of pests, and apply natural remedies as needed to keep pest populations in check. Providing a balanced ecosystem can help maintain pest control naturally.