Investigation On The Herbicidal Activity And Crop Safety To Maize Of QYC101

Maize is one of the most important grain crops with a large planting area and there are many kinds of weeds in corn fields,which seriously impair the yields and quality of maize.QYC101,a novel POST herbicide created by Qingdao Kingagroot Chemicals Co.,Ltd.belongs to new chemical class of pyrazolones.Now,QYC101 is under the herbicide registration process and it is still a new active ingredient in the Chinese market and even the world market.There is also no available research about the POST application of QYC101 for weed control in maize fields in China.Thus,this study has studied the herbicidal spectrum,herbicidal activity,safety to different maize varieties and the detoxification effect and detoxification mechanism of safeners to QYC101 in maize with series methods such as pot experiments in greenhouse,enzyme activity assays and field experiments.Moreover,the effect of different factors including temperature,rain and leaf stages of weeds on the efficiency of QYC101 were evaluated.The research aims to provide theoretical basis for the application of QYC101 in maize field.The results are as follows:The results of greenhouse experiments showed that QYC101 had high weeding efficency against common grass weeds and broadleaf weeds.The IC₅₀ vlues of QYC101 against Echinochloa crusgalli,Setaria viridis,Digitaria sanguinalis,Abutilon theophrasti,Amaranthus retroflexus were 3.35,2.71,2.63,2.54,1.15g a.i.ha^-1,respectively,and the IC₅₀values of mesotrione against the five weeds were 12.53,182.40,5.02,0.85,1.83 g a.i.ha^-1,respectively.The safety experiments of QYC101 to 22 maize hybrids showed that QYC101 QYC101was safe for maize along with some variations between maize hybrids.At the rate of 90 g a.i.ha^-1,the fresh weight inhibiting rates of 10 maize hybrids such as Jiachang 339,Liaodan 127,et al.were above 5%,but below 10%.The fresh weight inhibiting rates of 12 maize varieties such as Zhengdan958,Xianyu335,were below than 5%.The selectivity indexes of QYC101between Xianyu335 and Echinochloa crusgalli,Setaria viridis,Digitaria sanguinalis,Abutilon theophrasti,Amaranthus retroflexus were 21.81,15.32,3.00,6.71,30.18.The selectivity indexes of QYC101 between Denghai605 and five weed species were 40.83,28.685.61,12.56,56.50 and the selectivity indexes of QYC101 between Liyu31 and five weed species were 40.24,28.27,5.53,12.38,55.69.Compared with mesotrione,all selectivity indexes of QYC101 between maize and five weed species were higher except that between maize and Abutilon theophrasti.The results of environmental factors and weed leaf age on the efficacy of QYC101showed that the herbicidal activity of QYC101 to Echinochloa crusgalli increased with temperature increasing from 15 to 35°C.At 15°C/20°C（night temperature/day temperature）,20°C/25°C,25°C/30°C and 30°C/35°C,the IC50 values of QYC101 against Echinochloa crusgalli were 69.3031,7.5471,4.0014,2.7770g a.i.ha^-1,respectively.With rainfall after QYC101 post-emergence（POST）application,the herbicidal activity of QYC101 against Echinochloa crusgalli increases with the interval increased.With interval of 0h,0.5h,1h,2h,4h,8h,12h,24h,the IC₅₀ values were 4.798,3.8949,2.4273,2.1735,2.0788,1.9644,1.9471,1.7104g a.i.ha^-1,respectively.The efficacy of QYC101 was reduced with the increased growth stage of Echinochloa crusgall and the IC50 values are 0.0480,0.0157,0.1251,0.9542,3.4379,3.5418g a.i.ha^-1,respectively,when QYC101 applied at 1,2,3,4,5 and 6-leaf stages.The IC₅₀ value was 1.3651g a.i.ha^-1 with QYC101 pre-application at 0-leaf stage of Echinochloa crusgalli.The results of detoxification effect of safener on QYC101 showed that when mass radios（cyclopropanesulfonamide:QYC101）were 1:12,1:24 and 1:48,the plant height protection rates of the mixtures to maize were 117.3%,133.4%,131.1%,respectively,and the plant weight protection rates were 240.9%,269.0%,251.9%,respectively.When mass radios（isoxadifen-ethyl:QYC101）were 1:12,1:24 and 1:48,the plant height protection rates of maize are 116.6%,127.4%,125.6%,respectively,and the plant weight protection rates are155.8%,191.3%,206.3%,respectively.Compared with isoxadifen-ethyl,the detoxification effect of cyclopropanesulfonamide on QYC101 was better in maize.The study on the detoxification mechanism of cyclopropanesulfonamide to QYC101show that GSTs activity of maize applied with mixture of QYC101 with cyclopropanesulfonamide significantly increased compared with CK and QYC101 applied alone.Cyclopropanesulfonamide improves GSTs activity and the metabolic capacity of maize increases,which may be one of the important ways to improve the safety of QYC101 to maize.The results of field experiments further proved that QYC101 had good herbicidal effect against Setaria viridis,Digitaria sanguinalis,Abutilon theophrasti and Amaranthus retroflexus and was safe to Denghai618.With QYC101 POST application at the rates of 45g a.i.ha^-1,67.5g a.i.ha^-1,90g a.i.ha^-1,135g a.i.ha^-1,the total fresh weight efficiency was 87.5%,89.6%,91.4%,93.4%,respectively.When QYC101 at 67.5g a.i.ha^-1 mixed with atrazine at1140g a.i.ha^-1,halosulfuron-methyl at 20g a.i.ha^-1 and nicosulfuron at 45g a.i.ha^-1,the total fresh weight efficiency was 88.6%,94.0%,94.4%,respectively.The total fresh weight efficiency of contrast mixture of halosulfuron-methyl with nicosulfuron is 93.7%.In conclusion,the results taken together demonstrate that the novel structure herbicide QYC101 has great potential as an effective and safe agrochemical agent in weed management in maize production system.