Title: The Study of the efficacy of the Weedex herbicide on barnyardgrass control in transplanted rice
Author: Bijan Yaghoubi
Abstract: Barnyardgrass is the most important and abundant weed in rice fields in Iran, which yield loss alone up to 70 percent has been reported. Herbicides’ role in barnyard grass control is more than 90 percent, and all paddy fields are treated with at least one herbicide to control this weed. Sequential application of existing herbicides and introduce new herbicides with different mechanisms of action to maintain the efficiency of herbicides, avoid resistance, and stability of chemical management of the barnyard grass are necessary for the economic production of rice. Over the past few decades, more than 90 percent of the country’s paddy fields have been repeatedly treated with butachlor (machete) herbicides, which will be eliminated in the near future, and the introduction of new herbicides with different mechanisms of action is a priority. The experiment was conducted to evaluate the efficacy of Weedex (pendimethalin EC 50%) as one of the possible alternatives to a machete in weed control in transplanting rice with emphasis on barnyard grass control. Initially, in laboratory conditions, the response of water grass (E. oryzoides) seeds to 1, 0.1, 0.01, 0.001, and 0.0001% of the recommended dosage of Weedex compared to conventional herbicides pretilachlor (refit), machete, thiobencarb (Saturn), bensulfuron methyl (Londax DF 60%) and hand weeded and weedy control was investigated and in field studies in Gilan and Mazandaran provinces, the efficacy of Weedex dose including 500, 750, 1000, 1500 and 2000 (g ai.ha-1) insole application and mixing with Londax in comparison with the common herbicide combinations machete + Londax, refit + Londax, Saturn + Londax, hand weeded and weedy control were examined. According to the results of the first experiment, the Weedex herbicide up to 0.01% of the recommended dosage, had the same efficacy as machete, refit, and Saturn, and led to complete control of barnyard grass. In this experiment, Londax had the lowest efficiency and significantly different from other herbicides. The results of field studies showed that Weedex up to twice the recommended dose showed negligible phytotoxicity on rice and rice was able to recover quickly, which was superior to conventional herbicides in this respect. According to visual evaluation as well as the density and biomass of barnyard grass, Weedex had ≥95% efficacy in controlling this weed in field conditions and was similar or superior to common herbicides. Refit, machete, and Saturn have synergistic relationships with Londax, but physical mixing of Weedex with Londax is not recommended, but their sequential application is more effective at controlling the grasses, broadleaf, and sedges simultaneously. One of the special advantages of Weedex is that it can be used before transplanting, which has no adverse effects on rice and has acceptable efficiency in controlling barnyard grass. In terms of paddy rough rice yield, the Weedex was similar to the machete and other common herbicides and had no significant difference with hand weeded control. The dosage of Weedex (Pendimethalin EC 50%) to control barnyard grass in transplanted rice is recommended 1.5 to 2 liters of trade material.
Keywords: Drought, EMS, Phenotypic Diversity, Polyethylene Glycol, Mutation, Rice, Stress Index