Acaricidal Activity of Essential Oils from Lantana camara (Verbenaceae) and Ruta chalepensis (Rutaceae) against Oligonychus afrasiaticus (Acari: Tetranychidae)1

Abstract

Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae) is a major pest that causes significant economic losses to date palm, Phoenix dactylifera L. (Arecales: Arecaceae), fruit in southern Tunisia and Algeria, where climatic conditions are highly conducive to development of this insect. In our efforts to develop sustainable management alternatives for O. afrasiaticus, essential oils extracted from Lantana camara L. and Ruta chalepensis L. were tested against O. afrasiaticus adult females. Both essential oils exhibited acaricidal activity against O. afrasiaticus in laboratory bioassays of concentration–mortality responses. At 96 h after exposure, the median lethal concentrations were 5,259 μl/ml for the L. camara extract and 3,329 μl/ml for the R. chalepensis extract. Based on median lethal times, the acute toxicity of the extracts against O. afrasiaticus was higher with L. camara than with R. chalepensis at a concentration of 50 µl/ml. Gas chromatography–mass spectrometry analysis revealed that the primary constituents of the essential oil extracted from L. camara were humulene (26.65%), caryophyllene (26.33%), and γ-muurolene (14.22%). The predominant compounds in the essential oil obtained from R. chalepensis were 2-undecanone (50.52%), 2-nonanone (11.27%), and 2-octanol, acetate (9.17%). These two essential oils have potential for development as botanical acaricides for the management of O. afrasiaticus in date palm production in this region.