Bio-Based Insect Repellents from Guayule (Parthenium argentatum) Resin

Guayule resin, a byproduct of naturalrubber processing,may be a sustainable source of active ingredients for bio-based repellentsfor urban insects. Guayule (Parthenium argentatum)is an alternative source of natural rubber that grows well in aridand semi-arid regions. The feasibility of guayule as an industrialcrop is substantially impacted by the value of the rubber extractionbyproducts, resin and bagasse. In this study, guayule resin, a complexmixture of secondary plant metabolites, was tested as a bio-basedinsect repellent. Whole guayule resin and vacuum-distilled resin fractionswere tested against Turkestan cockroaches (Blatta lateralis Walker), both immediately after application and after being allowedto evaporate for one week. All resin fractions showed good repellencyin their fresh form, with two fractions performing better than thepositive control (citronella Java oil). The heavier resin fractions,which contain a mixture of lipid and oxygenated sesquiterpenes, demonstrateda persistent repellent activity against Turkestan cockroach nymphs,losing only & SIM;3% of their repellency after 7 days. The vacuum-distilledfractions were characterized by gas chromatography-mass spectroscopyand fatty acid methyl ester analysis. Structural similarity analysisshowed that the most abundant compounds in guayule resin overlap withsome active ingredients in commercial repellents. Techno-economicanalysis of guayule resin-based insect repellents showed that a substantialquantity would need to be produced and sold (& SIM;8% of the U.S.active ingredient market for residential insect repellents) in orderto achieve the targeted resin selling price of 1.00 USD/kg resin.