Evaluation of Chemical Compound of Thyme Essential Oil and Repelling and Lethality Effect of Thyme Plant Essential Oil on Rice Weevil

The use of plants, especially medicinal plants, for treating diseases and controlling pests biologically has increased significantly in recent years. Wild Mountain Thyme is one of these plants widely used in Iran, especially Khoy, Iran. Concerning the importance of this plant in the traditional medicine of the region and the need for controlling grain pests, we decided to study the plant’s chemical compounds, the antibacterial effects of its essential oil, and its repelling and lethality effect. Wild Mountain Thyme was collected from the southeast of Khoy in the spring and identified in the Institute of Forests and Pastures. The plant’s essential oil was extracted by distillation with water using a Clevenger machine. The resulting oil had a yellow color and a pungent smell, and its percentage was 1.64% compared to the dry weight of the plant. A total of 37 chemical compound was identified and isolated using a gas-mass chromatography device, the main of which was carvacrol (36.8%), thymol (36.8%), gamma-terpinene (10.6%), and paracymene (8.5%). The microbial test of the essential oil of the Thymus Fedtschenkoi plant was performed on three Gram-positive bacteria (E. faecalis, S. aureus, and B. anthracis) and three Gram-negative bacteria (P. aeruginosa, Sa. paratyphi, and E. coli). Thymus Fedtschenkoi plant essential oil was effective on all Gram- and Gram-negative bacteria except for Pseudomonas aeruginosa. In addition, plant essential oil’s repellent and lethal effect on rice weevil were evaluated in three repetitions with different concentrations. The highest removal rate was at the highest concentration of 25 μl and 72 hours. The lethal effect of the plant on the weevil was at a maximum concentration of 20 μl and duration of 72 hours. LC50 and LC90 of essential plant oil were calculated and determined based on probit analysis software. Based on the results, the plant essential oil can have a good effect in controlling the rice weevil pest both in the field and warehouse.