Optimizing dosage of sethoxydim and fenoxaprop-p-ethyl with adjuvants to control wild oat

Using adjuvants to optimize and increase the efficacy of herbicides is an acceptable manner to reduce herbicides undesirable impact on the environment. Therefore, to detect suitable adjuvants for sethoxydim or fenoxaprop-p-ethyl, two dose–response experiments were conducted separately. The treatments consisted of six doses of sethoxydim or fenoxaprop-p-ethyl with and without adjuvants of Frigate, Citogate and Adigor against wild oat (Avena fatua L.). Moreover, the surface tension of a range of concentrations of adjuvants and adjuvants + sethoxydim or fenoxaprop-p-ethyl aqueous solutions was determined. Lower and higher surface tension values were obtained with aqueous solution of Citogate and Frigate alone and with herbicides. When adjuvants were combined with herbicides, wild oat control was significantly increased and was more than when were used alone. Between evaluated herbicides, adjuvant receptivity for sethoxydim was higher than for fenoxaprop-p-ethyl. Among evaluated adjuvants, the addition of Frigate and Adigor had the lowest and the highest effect, respectively, on the performance of sethoxydim or fenoxaprop-p-ethyl in controlling wild oat, which supports the solubilizing nature of cuticular waxes by Adigor as a theory.

► Adjuvants enhance herbicide performance through mechanisms other than ST reduction of the spray solution. ► Adjuvant receptivity for sethoxydim was higher than for fenoxaprop-p-ethyl. ► Low HLB adjuvant work best with water insoluble herbicides. ► Between surfactants, surface tension decreased with decreasing EO number.