To Örebro University

Biocompatible nanodispersions of the micro- and nanoemulsion type based on lemon oil terpenes, polysorbates, water and glycerol were used for the formulation of pyrethrins, natural insecticides derived from the extract of chrysanthemum flower. The proposed pyrethrin containing water-in-oil (w/o) microemulsions could be diluted with aqueous phase to obtain kinetically stable oil-in-water (o/w) nanoemulsions ready to use in sprayers for plant protection. Structural characteristics of the micro- and nanoemulsions were evaluated by Electron Paramagnetic Resonance (EPR) spectroscopy, Dynamic Light Scattering (DLS), Small Angle X-Ray Scattering (SAXS) and electrical conductivity. Dynamic properties of the surfactants’ monolayer as evidenced by EPR measurements were affected by the water content, the nature of the surfactant and also the presence of the biocide in both w/o microemulsions and o/w nanoemulsions. DLS and SAXS experiments of the nanoemulsions indicated the existence of two populations of oil droplets dispersed in the aqueous phase, globular droplets of 36-37 nm in diameter and also larger droplets with diameters >150 nm. In addition, all the applied techniques for structural determination revealed participation of the biocide in the nanostructure. The insecticidal effect of the natural pyrethrin nanodispersions was evaluated in laboratory bioassays upon a target-insect pest, the cotton aphid Aphis gossypii Glover (Hemiptera: Aphididae) in eggplant and was found increased compared to the natural pyrethin emulsion.