In the present study, experiments were conducted to investigate fumigant toxicity of the essential oil from Achillea millefolium (Asteraceae) and Prangos ferulacea (Apiaceae) plants for adult grain weevil (Sitophilus granarius) and rice weevil (S. oryzea) in vitro conditions. The essential oils were isolated with the water distillation method by Neo-Clevenger apparatus. During the study 10% (v/v) doses of oils in 20 cc of compressed rubber-capped glass tubes were used. After 24 hours mortality rates of the essential oils were compared. For S. granarius the toxicity of A. millefolium (98.85%) was observed to be more effective than P. ferulace (28.73%). Similarly for S. oryzea, A. millefolium (100 %) was found much more toxic than P. ferulace (9.82%). At the results of the study the essential oil of the A. millefolium has been determined as a promising insecticidal component against both pests.