The Screening Of Suitable Herbicide In Four Kinds Of Medicinal Plants

This article records the screening of suitable herbicide for Platycodon, Codonposis,Angelica and Rehmannia and the analysis of the residue of Prometryne in these four kinds of medicinal plants.The results show that the suitable chemistry herbicide is Prometryne and the exact amount of it is between 0.8 kg(a.i.)/hm~2 and 1.6 kg(a.i.)/hm~2.The results of the two methods by GC-MS,internal standard method and external standard method which are used to measure the Prometryne in three-year-old Platycodon,Codonposis,biennial Angelica and annual Rehmannia, show no obvious difference.The fortified levels of standard Prometryne in the four kinds of medicine plants dry root are 0.01 mg/kg,0.10 mg/kg,1.00 mg/kg.Meanwhile,the respective amount of Prometryne:three-year-old Platycodon is 70.7-82.7%;three-year-old Codonposis is 80.5-88.7%;biennial Angelica is 83.5-90.8%;annual Rehmannia is 78.0-85.9%. All of these can correspond to the stand of pesticide residue.When the dosage of Prometryne in the fields of medicine plants is 0.8 kg (a.i.)/hm~2,the residues in the dry roots of three-year-old Platycodon is 0.0276 mg/kg; in three-year-old Codonposis is 0.0235 mg/kg;in biennial Angelica is 0.0368 mg/kg. While the dosage of Prometryne in the fields of medicine plants is 1.6 kg(a.i.)/hm~2, the residues in the dry roots of three-year-old Platycodon is 0.0358 mg/kg;in three-year-old Codonposis is 0.0342 mg/kg;in biennial Angelica is 0.0465 mg/kg. These residues are all in the acceptable range.When the dosage of Prometryne in the fields of annual Rehmannia is 0.8 kg(a.i.)/hm~2 the residues in the dry roots is 0.0427 mg/kg,lower than MRLs;When the dose of Prometryne in the fields of annual Rehmannia is 1.6 kg(a.i.)/hm~2 the residues in the dry roots is 0.0590 mg/kg,higher than MRLs.According to these results of above experiments,it is suggested that the dosage of Prometryne in the field of medicinal plants as Platycodon,Codonposis,Angelica should not be more than 1.6 kg(a.i.)/hm~2 and in the field of annual Rehmannia should be 0.8kg(a.i.)/hm~2 at most.