Comparative study of insecticidal activities of wild thyme species essential oils originated from South Western Morocco

The aim of this study was to compare for the first time the insecticidal activities of essential oils from different wild thyme species namely Thymus satureioides Coss., Thymus broussonetii Boiss., Thymus maroccanus Ball., Thymus ciliatus (Desf.) Benth., Thymus pallidus Batt., and Thymus leptobotrys Murb., originated from south and South Western Morocco. The insecticidal activity of essential oils isolated from Moroccan thyme was evaluated using the contact toxicity assay. The results showed that all essential oils tested presented important insecticidal activity against adults of Tribolium castaneum Herbst. While the oil extracted from Thymus leptobotrys (carvacrol-rich oil) exhibited the highest toxicity, with LD50 (lethal dose that kill 50% of the exposed insects) and LD90 (lethal dose that kill 90% of the exposed insects) values of 0.08 μl/cm2 and 0.19 μl/cm2, respectively and LT50 (lethal time required to kill 50% of the exposed insects) and LT90 (lethal time required to kill 90% of the exposed insects) values ranged from 32.80 to 17.18 h and from 69.37 to 32.05 h, respectively. The current results suggest that the contents of Moroccan thyme essential oils particularly those obtained from Thymus leptobotrys have a good potential to be used as botanical bioinsecticide against Tribolium castaneum Herbst., the most important stored pests in North Africa.