Toxic, Oviposition Deterrent and Oxidative Stress Effects of Thymus vulgaris Essential Oil against Acanthoscelides obtectus.

The bean weevil Acanthoscelides obtectus Say (Coleoptera: Chrysomelidae: Bruchinae) can cause significant losses in production of its primary host common bean Phaseolus vulgaris L. To avoid bean protection with environmentally risky chemical insecticides and provide sustainable and safe production of food, new pest management methods based on natural compounds are investigated. In the present study, we evaluated protective potential of the essential oil (EO) from the common thyme Thymus vulgaris L. applied on bean seeds. We assessed residual contact toxicity of thyme EO and its effects on A. obtectus longevity, oviposition and adult emergence. Furthermore, to elucidate the role of oxidative stress in thyme EO toxicity, we estimated the levels of oxidatively damaged proteins and lipids, as well as the level of thiols which have important role for antioxidant capacity. We found that thyme oil significantly reduced adult survival and longevity, induced oxidative damage to lipids and proteins and depleted protein and non-protein thiols in a concentration-dependent manner. Females appeared to be more tolerant to thyme oil treatment than males. Sublethal EO concentrations affected oxidative stress indices, deterred oviposition and strongly inhibited adult emergence. The results suggest that thyme oil has the potential to be used as an ecofriendly insecticide for A. obtectus control.