Naturally occurring bioactive compounds from four repellent essential oils against #Bemisia tabaci# whiteflies

BACKGROUND: In tropical countries, netting is an effective sustainable tool for protecting horticultural crops against Lepi- doptera, although not against small pests such as Bemisia tabaci , while smaller mesh netting can be used in temperate regions. A solution is to combine a net with a repellent. Previously we identified repellent essential oils: lemongrass ( Cymbopogon citra- tus ), cinnamon ( Cinnamomum zeylanicum ), cumin ( Cuminum cyminum ) and citronella ( Cymbopogon winternarius ). The present study was designed to identify the active compounds of these essential oils, characterise their biological activity and examine theirpotentialforcoatingnets.Weinvestigatedtheefficiencyandtoxicityofnetsdippedindifferentsolutions.Wethenstudied the repellent effect with an olfactometer and the irritant effect by videotracking. RESULTS: Geraniol and citronellol were the most promising net coatings owing to their repellent effect. The repellency, irritancy or toxicity varied with the product and concentration, and these features were independent, indicating that the repellent and theirritant/toxicmechanismswerenotthesame.Thecombinedeffectsofthesedifferentcompoundsaccountforthebioactivity of the mixture, suggesting interactions between the compounds. CONCLUSION:Thisnewsustainablestrategyforprotectingvegetablecropsagainstwhitefliesisdiscussed,inadditiontotheuse of companion plants that could produce such bioactive compounds. (Résumé d'auteur