Insecticidal effects of essential oils of eleven plant species from Lamiaceae on Sitophilus granarius (L.) (Coleoptera: Curculionidae)

Abstract

Four different concentrations of the essential oils obtained from eleven plant species (Origanum onites L., Origanum rotundifolium Boiss., Rosmarinus officinalis L., Salvia hydrangea Dc., Salvia numerosa L., Salvia multicaulis Vahl., Salvia sclarea L., Satureja hortensis L., Satureja spicigera (C. Koch) Boiss., Thymus fallax Fisch. & Mey. and Thymus sipyleus Boiss.(Lamiaceae) were tested against adults of Sitophilus granarius (L.) on Petri dishes. After exposure, mortality of the adults was determined at 24, 48 and 96 h. The results show that essential oils of O. onites, O. rotundifolium, R. officinalis, S. hydrangea, S. hortensis, S. spicigera, T. fallax and T. sipyleus have an insecticidal effect on adults of S. granarius in comparison with controls. The insecticidal effect was influenced by the doses of the essential oils and the exposure time. Higher doses and longer exposure time resulted in maximum toxicity on S. granarius. Treatment with essentials oils of O. onites, O. rotundifolium, R. officinalis, S. hydrangea, S. hortensis, S. spicigera, T. fallax and T. sipyleus leads to a higher and S. multicaulis to less mortality of adults of S. granarius but essential oils of S. numerosa and S. sclarea had no effect. The mortality rates after 96 h of treatment with the maximum dose (20 µl) of essential oils of S. hortensis, O. rotundifolium, O. onites, S. spicigera, R. officinalis, T. fallax T. sipyleus, S. hydrangea, S. multicaulis, S. sclarea and S. numerosa was determined as 100, 96.97, 95.27, 94.27, 93.93, 88.88, 82.82, 67.33, 55.21, 41.76 and 39.73 % for S. granarius, respectively. Separately, the mortality rates after 96 h of treatment with the 1 µl in dose of essential oils of S. hortensis was established to the highest mortality rate in S. granarius with 97.97 %, and 5, 10 and 20 µl in dose of S. hortensis with 100 %.