Stability of the oil-based nanoemulsion of Laureliopsis philippiana (Looser) and its insecticidal activity against tomato borer (Tuta absoluta Meyrick)

Tuta absoluta is one of the most serious pests of tomatoes worldwide. The current strategies of pest control for T. absoluta include essential oils (EOs) and its formulations. Biological activity of Laureliopsis philippiana essential oil, a tree species native from Chile, has been demonstrated against pests. Hence, the aims of this study were to determine the stability of the L. philippiana oil-based nanoemulsion (NE) and to evaluate the insecticidal effects of pure and NE forms of the essential oil against T. absoluta. Emulsion stability was measured over a 35-day period, with measurements conducted every 7 days, while the efficacy of the NE to control T. absoluta was compared to that of the pure EO. The results indicate that the NE remained stable during the whole evaluation period, averaging at the end of the experiment a particle size of 40.60 nm, zeta potential of - 14.54 mV, polydispersity index (PDI) of 0.30 and a pH level of 4.64. The L. philippiana NE after 4 h fumigation showed greater insecticidal activity against T. absoluta than pure EO of, with LC50 and LC90 values of 4.6 and 27.8 mu L L-1, whereas the EO resulted in values of 27.1 and 75.3 mu L L-1, respectively. These results are the first report of the insecticidal properties of the EO of L. philippiana against T. absoluta. The biological activity exerted by the oil was significantly enhanced when developed as a NE as it remained stable for more than four weeks and was much more efficient in the control of T. absoluta than pure EO, particularly at low concentrations. The use of L. philippiana essential oil for sustainable agriculture presents a promising strategy in the seek of new insecticide products.