Acaricidal and molluscicidal potential of three essential oils isolated from Egyptian plants

The chemical composition of essential oil isolated from Eucalyptus camaldulensis Dehnh was analyzed by gas chromatography/mass spectrometry (GC/MS). Acaricidal and molluscicidal activities of this oil and the essential oils of Mentha microphylla C. Koch and Lantana camara L. were evaluated against adults and eggs of the two-spotted spider mite, Tetranychus urticae Koch, and terrestrial snails, Theba pisana and Eobania vermiculata. To determine the effects of the essential oil vapors against the adults of T. urticae, concentrations of 1, 2.5, 5 and 10 µl / l air were tested. Responses varied with essential oil, dose and exposure time. Mentha microphylla oil exhibited the strongest acaricidal activity at all of the tested concentrations followed by E. camaldulensis oil, while L. camara oil showed the weakest one. At concentrations of 1 and 2.5µl / l, M. microphylla oil caused 76.67 and 100 % mortalities after 48h of treatment, respectively. In a leaf disc dipping assay with eggs of T. urticae, the essential oil of M. microphylla revealed also the highest activity with LC50 value of 137.51µg / ml, whereas the essential oil of L. camara showed the lowest activity with LC50 value of 272.27 µg / ml. This study may suggest that these essential oils have potential to be used for management of T. urticae under greenhouse conditions. In addition, the essential oils of L. camara and M. microphylla exhibited pronounced molluscicidal activity against T. pisana snails. The oil of L. camara showed molluscicidal activity greater than methomyl as a reference at all of the tested concentrations.