Differences in essential oil content of berries and leaves of Solanum sarrachoides (Solanaceae) and the effects on oviposition of the tomato spider mite (Tetranychus evansi)

Essential oils from leaves and berries of Solanum sarrachoides were obtained by hydro-distillation, analyzed by GC–MS and tested for oviposition deterrence against Tetranychus evansi. Plant oils comprised mainly of monoterpenes and fatty acids, but differed in terms of their relative abundance. The leaf oil contained mainly camphor (34.1%), limonene (8%), decanoic acid (9.3%) and hexadecanoic acid (7.3%). The berry oil contained mainly fatty acids (>20%) including hexadecanoic acid (9.8%) and dodecanoic acid (5.9%), hydrocarbons (>10%) and (E)-β-linalool (3.1%). In oviposition deterrence assays, the leaf essential oil and individual major monoterpenes compared favorably with the two positive controls, neem oil and cinnamaldehyde at varying concentrations [incidence ratio (IR) < 1]. Compared to the fatty acid blend, the monoterpene blend exhibited strong oviposition deterrence (IR < 1) across all concentrations. Our results show that essential oils of S. sarrachoides and their monoterpene constituents play a role in regulating oviposition in T. evansi.

► Solanum sarrachoides belongs to S. section Solanum. ► Chemical composition of S. sarrachoides essential oils were analyzed. ► Essential oils and their major constituents were tested against Tetranychus evansi. ► Plant oils comprised varying amounts of monoterpenes and fatty acids. ► Leaf oils and major monoterpenes were the most effective oviposition deterrents.