Insecticidal Effects of Essential oil and plants Extract of Thymus daenensis on Sitophilus oryzae L. (Col.: Curculionidae)

In the recent years, extensive research is done on various herbal combinations to find less dangerous effective alternatives for chemical insecticides to control stored products pests. In this research, the insecticidal effects of Thymus daenensis essential oils and extracts against rice weevil adults were investigated in laboratory condition. Essential oils was extracted through distillation with water using Clevenger apparatus and methanol extract of this plant was prepared. Tests of randomized complete block included six concentrations and three replications for essential oils (fumigant toxicity) and five concentrations and three replications for extract (contact toxicity) along with control treatment for both in condition of 27±1ºC degrees Celsius temperature, relative humidity of 65 ± 5 percent and darkness. LC50 values were calculated by SPSS.21.0 software which presented the value of LC50 of Thymus daenensis essential oils after 48 hours, 138.90 ± 0.43 ?l/l air and the value of extract after 7 days were calculated 15.37 ± 0.09 ?l/l air on rice weevil adults. According to the results found from GC-MS, Twenty-six chemical combinations were identified in Thymus daenensis essential oils which included Thymol (52.24%), and Ispropyl-1-methoxy-4-methylbenzen (6.40%) as the highest existing amounts in this plant. Results showed that increasing the concentration of essential oils and extracts increased the mortality rate in both cases. The results also showed that essential oils and extracts of Thymus daenensis are effective biological sources which can effectively protect stored grain from infestation by the rice weevil; although for application of these combinations further research may be needed.

insecticidal effects, essential oil, plant extract, Thymus daenensis, Sitophilus oryzae