Isofuranodiene microemulsions as novel larvicides to manage Culex quinquefasciatus mosquito vectors

In recent years, there is a growing interest towards the employ of eco-friendly pesticides based on natural products. In this regard, plants represent a great reservoir of chemicals with high potential of exploitation in this field. Isofuranodiene, a bioactive furanosesquiterpene occurring as the major volatile compound in the Smyrnium olusatrum essential oil, has a noteworthy potential to be used as a botanical insecticide. However, its low solubility together with susceptibility to oxidation and thermal degradation limit its application on a wide scale. To face these challenges, herein isofuranodiene was encapsulated in microemulsions (MEs) as an effective tool to stabilize its physico-chemical properties. Isofuranodiene concentration in MEs was 0.75% and 0.375% w/w. The ME insecticidal activity was assessed against 3rd instar larvae of Culex quinquefasciatus mosquitoes. The impact of ME-based larvicidal treatment as sub-lethal concentrations on adult emergence was also evaluated. Furthermore, to shed light on potential ecotoxicology risks for non-target invertebrates, the MEs were tested on the aquatic microcrustacean Daphnia magna as well as on adult earthworms, Eisenia fetida. Results highlighted that stable isofuranodiene MEs are highly effective against Cx. quinquefasciatus larvae, with little impact on non-target species, outlining their potential as to develop larvicides for vector control programs.