Fumigant Toxicity of Essential Oils Extracted from Three Medicinal Plants Against Callosobruchus maculatus Adults (Coleoptera: Bruchidae)

Fumigant toxicity of essential oils from Foeniculum vulgare (Apiaceae), Teucrium polium (Lamiaceae) and Satureja hortensis (Lamiaceae) were evaluated against the adults of cowpea seed beetle, Callosobruchus maculatus exposed for 24h. Essential oils were obtained through steam-distillation using a Clevenger-type apparatus. Bioassays were conducted at 28±2 °C and 60±5% R.H. in dark conditions. Six concentrations of each oil were utilized each in six replications. Gas chromatography coupled with mass spectrometry was applied to identify the main components of the essential oils. The principal constituents of F. vulgare oil consisted of E-anethole (60.61%) and Fenchone (12.14%) while those of T. polium oil were piperitenon oxide (21.72%), α-pinene (11.33%) and carvon (11.29%). S. hortensis oil mainly consisted of carvacrol (50.13%) and thymol (27.77%). All the essential oils exhibited high fumigant activity against C. maculatus adults. The results indicated that mortality of 1-day-old adults increased with oil concentration. Males were more susceptible to the oils than females. The essential oil extracted from F. vulgare proved to be most toxicant with LC50 values of 21.31 and 29.45 µL L-1 of air against male and female pests, respectively. The LC50 values of T. polium oil were recorded as 54.63 and 80.75 µL L-1 of air, while the corresponding values of S. hortensis oil were 74.36 and 156.66 µL L-1 of air against male and female pests, respectively. The results demonstrated that the essential oils of these plants, especially those of F. vulgare can be considered as potentially effective control agents against cowpea seed beetle.