Toxicity of essential oil vapours obtained from several plants species against the granary weevil, Sitophilus granarius (L.).

Essential oil vapours from Thymus spicata, Thymbra spicata var. spicata, Mentha spicata var. formasa and Mentha spicata subsp. tomentosa were tested for their toxicity against the adults of Sitophilus granarius (L.). Essential oils were applied at the doses of 2, 3 and 4 mu l in desiccators with 4 1 capacity, corresponding to 0.5, 0.75 and 1 mu l/l air. Although desirable insecticidal activities against the pest were achieved with all the essential oils tested, the oil of M. spicata subsp. tomentosa was found the most effective at a dose of 0.5 mu l/l air and an exposure period of 48 h. On the other hand, the oils from M. spicata subsp. tomentosa and M. spicata var. formasa had similar effects at the doses of 0.75 and 1 mu l/l air and the exposure periods of 24, 36 and 48 h. For each of the plant essential oils tested, the toxicity against adult S. granarius was dose- and exposure time-dependent. A 100% mortality rate in adult S. granarius was achieved only with M. spicata subsp. tomentosa and M. spicata var. formasa essential oils at the dose of 1 mu l/l air and the exposure periods of 36 and 48 h. It can thus be concluded that essential oils from M. spicata subsp. tomentoso and M. spicata var. formasa may be potential control agents against S. granarius in storage facilities.