Control caterpillars on Plumeria by handpicking them from the plant, especially if the infestation is small. Prune and dispose of heavily infested plant parts. Use biological control methods, such as introducing parasitic wasps or beneficial nematodes, to target caterpillars naturally. If necessary, apply Bt (Bacillus thuringiensis) insecticides, which specifically target caterpillars and are safe for beneficial insects and humans. Regularly inspect the plant for signs of caterpillars and treat promptly.