Environmental risks resulting from the increasing application of chemical herbicides have raised many concerns about human health and the safety of agro ecosystems and environment. Hence, it is very important to find practical and effective methods for reducing the use of pesticides in environment as well as the increasing the efficiency of these compounds. Addition of adjuvants to spray solutions could be considered as one of these methods. Greenhouse studies were conducted using a complete randomized design with a factorial arrangement during 2015-2016 to evaluate the impact of different adjuvants (citogate, canola oil, and castor oil) at concentrations of 0.1 and 0.2 (%v/v) with 5, 10, 20, 30 and 40 g a.i. ha -1 of tribenuron methyl herbicide to control common lambsquarters. Results showed that all applied adjuvants enhanced the efficacy of tribenuron methyl in decreasing the biomass of common lambsquarters. Efficacy of this herbicide increased with enhancing its concentrations. The required dose of herbicide to give 50 per cent common lambsquarters control (ED50) for no adjuvant, citogate, castor oil, and canola oil application (0.2 (%v/v)) was 21.24, 11.48, 11.65, and 11.81 g a.i. ha -1 , respectively. Totally the application of citogate and canola oil had the highest and the lowest impact on tribenuron methyl performance to control of common lambsquarters respectively. Also, the Relative Potency values were significantly increased when adjuvants were added to this herbicide. The results revealed that the use of citogate and vegetable oils can increase the efficiency tribenuron methyl, and reduce the application rate of this herbicide in agro ecosystems.

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