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

Guayule (Parthenium argentatum) is an alternative source of natural rubber that grows well in arid and semi-arid regions. The feasibility of guayule as an industrial crop is substantially impacted by the value of the rubber extraction byproducts, resin and bagasse. In this study, guayule resin, a complex mixture of secondary plant metabolites, was tested as a bio-based insect repellent. Whole guayule resin and vacuum-distilled resin fractions were tested against Turkestan cockroaches (Blatta lateralis Walker), both immediately after application and after being allowed to evaporate for one week. All resin fractions showed good repellency in their fresh form, with two fractions performing better than the positive control (citronella Java oil). The heavier resin fractions, which contain a mixture of lipid and oxygenated sesquiterpenes, demonstrated a persistent repellent activity against Turkestan cockroach nymphs, losing only ∼3% of their repellency after 7 days. The vacuum-distilled fractions were characterized by gas chromatography–mass spectroscopy and fatty acid methyl ester analysis. Structural similarity analysis showed that the most abundant compounds in guayule resin overlap with some active ingredients in commercial repellents. Techno-economic analysis of guayule resin-based insect repellents showed that a substantial quantity would need to be produced and sold (∼8% of the U.S. active ingredient market for residential insect repellents) in order to achieve the targeted resin selling price of 1.00 USD/kg resin.