Human health problems and environmental hazards caused by the indiscriminate use of chemical pesticides during the past three decades, led scientists to look for less persistent and biodegradable alternatives. Essential oils from aromatic plants are recognized as proper alternatives. In this experiment, toxicity of Satureja hortensis essential oil that was isolated via hydrodistillation was investigated against 1 to 7 day-old adults of the red flour beetle, Tribolium castaneum (Herbst), 12 to 14 day-old larvae of the Mediterranean flour moth, Ephestia kuehniella (Zell.) and Indianmeal moth, Plodia interpunctella (Hübner). Repellency of this oil on all the three pest species adults was also studied. After 48 h of exposure, the LC50 value for T. castaneum was 192.35 μl/L. LC50 values were calculated as 80.9 μl/L and 139.8 μl/L after 9 h for E. kuhniella and P. interpunctella, respectively. S. hortensis oil showed more contact toxicity against P. interpunctella (LC50 = 0.19 μl/cm2) than E. kuehniella (LC50 = 0.27 μl/cm2). Repellency of this oil on all the insect species was high. Relationship between exposure time and oil concentration on mortality of all species indicated that mortality was increased by increasing the oil concentration and exposure time.

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