PROBLEM TO BE SOLVED: To provide a new resistant derivative effective for pests causing feeding damage and useful as a pest control agent, and a pest control method for plants using the resistant derivative.SOLUTION: A pest-resistant derivative containing loliolide, epiloliolide or these mixture as an active substance; the pest-resistant derivative deriving resistance for Arguloida insects or spider mites; a pest control method for plants making contact or absorb a plant body either of the pest-resistant derivative mentioned above; the pest control method for plants mentioned above preventing the Arguloida insects or spider mites; and either of the pest control method mentioned above that the plant body is a solanaceous plant or a cruciferous plant.
