Effect of Six Herbicides on Weeds at Seedling Stage of Onion and Their Selectivity Evaluation
This study aimed to explore the effects of different herbicides on weeds and growth and development of onion seedlings,and provided a basis for the selective application of herbicides in onion fields.Therefore,we taked six herbicides to carry out field trail,which were 4 pre-emergence herbicides including bromoxynil octanoate 30％EC,clethodim 30％EC,quizalofop-P-ethyl 20％EC and 2,4-D 70％AS and 2 post-emergence herbicides including oxyfluorfen·metolachlor·pendimethalin 55％EC and pendimethalin 330 g/L EC.And then we also sprayed these six herbicides at pre-and post-emergence stages to determine their selectivity to onion in lab,field weeding efficiency and growth of onion seedlings.The results showed that these six herbicides had different selectivity to onion seedlings in lab.Bromoxynil octanoate 30％EC,clethodim 30％EC and quizalofop-P-ethyl 20％EC showed no or slight injury on seedlings of onion,and their leaves and plants grew normally.2,4-D 70％AS produced 3 levels injury on onion.Oxyfluorfen·metolachlor·pendimethalin 55％EC had little effect on the emergence rate,and the seedlings grew strongly in the later stage.Pendimethalin 330 g/L EC lead to a negative influence on the emergence rate and produced injury of 1-2 levels.Plant control effects of 6 herbicides on onion seedlings exited differences in fields.The fresh weight control effects on dicot weeds such as Oxybasis glauca and Capsella bursa-pastoris were more than 90％at 35 days and that were more than 70％at 50 days applied bromoxynil octanoate 30％EC.2,4-D 70％AS showed poor fresh weight control effect on all kinds of weeds.Clethodim 30％EC and quizalofop-P-ethyl 20％EC showed excellent fresh weight control effect on gramineous weeds such as Setaria viridis,Echinochloa crusgalli and Beckmannia syzigachne.Clethodim revealed good effect within 35 days,and quizalofop-P-ethyl revealed good effect in a longer time.Oxyfluorfen·metolachlor·pendimethalin 55％EC,a post-emergent herbicide,could well inhibited the growth of all kinds of weeds.Meanwhile,onion seedlings was dwarf at 35 d,but their growth was stronger than CK at 50 d.The control effect of pendimethalin 330 g/L EC was not as good as that of oxyfluorfen·metolachlor·pendimethalin 55％EC because of inhibiting onion seedlings growth,so the herbicide was not suitable for application.In summary,bromoxynil octanoate 30％EC with 1 125 mL/hm2 had a good control effect on dicot weeds,clethodim 30％EC with 480 mL/hm2 and quizalofop-P-ethyl 20％EC with 255 mL/hm2 had a good control effect on gramineous weeds,and oxyfluorfen·metolachlor·pendimethalin 55％EC with 1 650 mL/hm2 could be applied as a pre-emergent herbicide at seedling stage,which could have a selective and better weeding effect.
onion seedlingherbicideselectivityweeding effectagronomic character
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