Toxicity, development and physiological effect of Thymus vulgaris and Lavandula angustifolia essential oils on Xanthogaleruca luteola (Coleoptera: Chrysomelidae)

Abstract

Effects of essential oils from garden thyme Thymus vulgaris L. and lavander Lavandula angustifolia L. on mortality of third instar larvae, development of treated larvae, adult emergence and activity of digestive enzymes of elm leaf beetle Xanthogaleruca luteola Müller (Coleoptera: Chrysomelidae), were determined under laboratory conditions. The LC₅₀ values on third instar larvae were estimated at 0.3% and 0.63 %, respectively. Greater mortality was observed with increasing concentration of essential oils. Both essential oils disrupted the development of treated larvae, significantly decreased adult emergence as compared to untreated larvae. Present results also indicated that when larvae fed on treated leaves, activity level of digestive enzyme decreased in their midguts. Based on this study, essential oils derived from T. vulgaris possessed the greatest effect on larval development and activity level of digestive enzymes.