Study On The Phytotoxicity And Three Safeners-conferred Detoxification Of Bispyribac-sodium In Rice

The influence of bispyribac-sodium on rice has been studied in this experiment, including effect of bispyribac-sodium on different growth periods of rice, the main causes leading to reduction of rice output, and effect on rice seedlings of bispyribac-sodium at different rates.Three safeners were used to alleviate the phytotoxicity of bispyribac-sodium to rice in this paper.Finally, it was determined if abovementioned safeners could negatively affect its control effect on three main weeds in rice fields. Results were showed as follows:(1) Bispyribac-sodium promoted root growth at a low rate of 0.65mg/m L, conversely, produced inhibition in both root and shoot growth at a rather increased rate. The inhibitory effect on shoots and roots was enhanced with the increased rate of bispyribac-sodium. Field experiment showed bispyribac-sodium inhibited seedling growth 20 d after herbicide treatment while there is no significant influence on seedling tillering, although its tillering was progressed 10 d after herbicide treatment. Furthermore, Seed setting rate, effective panicle number and 1000-grain weight were significantly affected. The output was reduced by 30.6% compared to the control when bispyribac-sodium applied at 150g/hm2. Therefore, three factors comprising seed setting rate, effective panicle number and 1000-grain weight mainly caused a reduction in rice output.(2) The field test showed detoxification was related to dosage of antidotes. Plants were not significantly affected in height in contrast to herbicide treatment 20 d after treated by three safeners, while achieving evident recoveries 30 d later. Ligusticum Chuanxiong Extract at1500g/hm2 and fenclorim at 37.5 and 150g/hm2 delivered the best recovery rates in height,respectively corresponding to 74.48, 92.48 and 78.55%. Less than 40% of recovery rate was achieved by isoxadifen-ethyl. There is no obvious trend in rice tillering change after treated by safeners which needs further validation.(3) Three safers showed a certain detoxification, played a most important role in recovery rates in effective panicle number, conferred lesser impact on recovery rates in 1000-grain weight and barely affected seed setting rate, then leading to recovery in rice output. Detoxification of bispyribac-sodium was positively correlated to rates of Ligusticum Chuanxiong Extract and isoxadifen-ethyl, and negatively correlated to rates of fenclorim. Ligusticum Chuanxiong Extract.Fenclorim and isoxadifen-ethyl applied at 1500, 600 and 37.5g/hm2 respectively showed the best detoxification of bispyribac-sodium(150g/hm2). Fenclorim is the best one of them detoxified bispyribac-sodium in rice at 37.5g/hm2 with recovery in output increased up to 51.4%.(4)Bispyribac-sodium was highly active in elimination of monocots in rice field, fast in eliminating barnyard grass(Echinochloa crusgalli(L.) Beauv.) with acceptable endurance, while slow in eliminating Asian sprangletop(Leptochloa chinensis(L.) Nees) in early stage and fast in late stage. Three safeners didn't significantly and negatively affect Herbicidal effect of aforesaid weeds, while the herbicidal effect on those weeds was positively enhanced when isoxadifen-ethyl or fenclorim applied at 600 g/hm2 or 37.5g/hm2. Mode of action of safeners needs further experiments to validate.