Title: Investigating the effect of Arosgold Herbicide (Pirazosulfuronatel + Pertilachlor, DF 30.75%) on rice weed control sheath blight in field conditions
Author: Bijan Yaghoubi
Abstract: The efficacy of Eros Gold (pyrazosulfuron ethyl + pretilachlor, DF 30.75%) herbicide in transplanted rice weed control in the research fields of Rice Research Institute of Iran (Rasht and Amol) in the crop season of 2018 was investigated. The aim of this study was to study the efficacy of this herbicide in weed control and its phytotoxicity or selectivity on Hashemi rice in comparison with common herbicides. The investigated treatments included 0, 50, 100, 150, and 200% of the recommended dosage of Erosgold (about 550 g of active ingredient per hectare) and common herbicide treatments of paddy fields in Iran including butachlor + bensulfuron methyl (bensulfuron), pretilachlor + bensulfuron, thiobencarb + bensulfuron, triafamone + ethoxysulfuron and hand weeded control. Herbicides toxicity on rice and their effectiveness in controlling weeds at 2, 4, and 6 weeks after application of herbicides were evaluated visually. In addition, biomass, the density of weeds and dry weight, and tiller of rice were measured or counted at 4, 6, and 12 weeks after herbicide application. The results showed that in both experimental sites, more than 98% of weeds were related to barnyard grass (Echinochloa crus galli) and bulrush (Bolboschoenus planiculmis). The investigated treatments had little toxicity on rice (≤12%) which was recovered early. The density and biomass of weeds in Mazandaran was less than 20% of Guilan and the efficiency of all treatments was ≥95%. The efficiency of all doses of the new herbicide Erosgold in Guilan in reducing the density and biomass of barnyard grass and bulrush in all evaluation stages was significantly lower than conventional herbicide treatments. In addition, in this province, the dry weight and panicle number of rice in treatment with different dosages of Erosgold herbicide were always less than conventional herbicides. The rice yield loss in weedy control treatments was 25% and 67% in Mazandaran and Guilan provinces respectively. Rice yield in Mazandaran was statistically similar in all treatments except weedy control, which can be attributed to low weed competition and good performance of herbicides at lower densities of weeds. Grain yield in all dosages of Erosgold herbicide in Guilan was significantly lower than the common herbicides. Overall, the results of this experiment in Mazandaran are not valid enough to make a decision about the new herbicide Erosgold registration, because the weed density in that province was much lower than normal and the effectiveness of all herbicide treatments in reducing weed density and biomass, even 50% of recommended dosages of Erosgold was about 100%, while in Guilan, not only the efficacy of 50% but also the efficacy of 200% the recommended dosage of Erosgold was not sufficient in weed control and was significantly lower than other herbicides studied. The efficacy of Erosgold at all dosages studied in the control of barnyard grass and bulrush in Guilan at all stages of sampling was significantly lower than conventional herbicides. In addition, in Guilan, biomass, the number of tiller and rice panicles in treatments related to Erosgold herbicide dosages were always significantly lower than conventional herbicides and hand weeded control. Another herbicide that is completely similar to Erosgold and is the result of mixing pyrazosulfuron ethyl + pretilachlor with the trade name of pirazchlor (TB 17%) has been registered in Iran and the above herbicide had the similar efficiency as the common herbicides studied in the present study. Therefore, due to the inefficiency of Erosgold in comparison with common herbicides and the existence of herbicides with active ingredients and mechanism of action similar to Erosgold in the country, based on the results of the present study, Erosgold is not suitable for introduction to control rice weeds.
Keywords: Mixing of Herbicides, Barnyard grass, Bulrush, Paddy, Old Herbicide, New Herbicide