Sepiolite-rosemary oil combination as an environmentally oriented insecticide

Pest management is essential for cost-effective agriculture, however, due to the pests' ability to develop resistance to pesticides and the environmental and health considerations, there is a need for new and less hazardous alternatives. Certain essential oils that are regularly consumed by humans, are known to be lethal to specific pests and may serve as an alternative to traditional pesticides, even though their rapid volatility and potential phytotoxicity limit their direct use. Clays and organoclays were suggested as matrices for controlled-or slow-release of organic compounds, and thus might increase the pesticide efficiency and reduce the phytotoxicity of essential oils, by influencing their release. This study combined in vitro studies evaluating the rate of evaporation of rosemary (Rosmarinus officinalis) or lemongrass (Cymbopogon citratus) essential oils (ROEO and CCEO, respectively) from clay-based formulations, with in vivo experiments of essential oil-sepiolite insecticides on onion thrips (Thrips tabaci) while avoiding phytotoxicity damage to chives' (Allium schoenoprasum) crops. Fourier transform infrared spectroscopy (FTIR) and gravimetric kinetic measurements of the evaporation led to the conclusion that sepiolite increased the half-life evaporation period when compared to the raw essential oils or oils pre-adsorbed to other clays or even organoclays. Gas chromatography measurements showed that the interaction with the clay yielded differences in evaporation for the different components in the ROEO oil. Lethality tests of canola:essential oil combinations indicated that ROEO is effective at very low ratios, whereas CCEO activity required higher ratios. Plant tests showed that while the efficiency of CCEO formulation was not very significant, binding ROEO to sepiolite reduced its phytotoxicity yielding efficient pesticidal activity on thrips with less damage to chives' plants even one month after application.