Susceptibility of Two Sitophilus species (Coleoptera: Curculionidae) to Essential Oils from Foeniculum vulgare and Satureja hortensis

This study was conducted to determine the insecticidal activity of essential oils from Fennel, Foeniculum vulgare (Apiaceae), and Summer savory, Satureja hortensis (Lamiaceae), against two stored-product insects. Essential oils from two species of plants were obtained by Clevenger- type water distillation and their fumigant toxicities were tested against adults of the wheat weevil, Sitophilus granarius and rice weevil, Sitophilus oryzae (Curculionidae). The mortality was determined after 24 and 48 hrs from beginning of exposure. LC50 values of each essential oil were estimated for each insect species. Fumigation bioassays revealed that essential oils from two plants had strong insecticidal activity on experimental insects. LC50 values indicated that S. granarius was more susceptible than S. oryzae to essential oils at the exposure time 24 and 48 hrs. The mortality effect of S. hortensis oil was lower than F. vulgare oil. The LC50 values decreased with the duration of exposure to the essential oil concentrations. In all case, responses varied according to plant material, concentration, and exposure time. These results indicated that essential oils from S. hortensis and F. vulgare could be applicable to the management of stored product insects to decrease ecologically detrimental effects of utilization synthetic insecticides.