Abstract: 【Objective】 The objective of this study was to investigate the resistance level of Alopecurus japonicus Steud. to haloxyfop-R-methyl, which is an ACCase inhibitor belonging to aryloxyphenoxypropionates (AOPPs), and its cross-resistance level to other herbicides with the same target site. A. japonicus seeds were collected from different oilseed rape fields where haloxyfop-R-methyl had been continuously applied for different years. 【Method】 The resistance level of A. japonicus to haloxyfop-R-methyl were evaluated by seed-bioassay and whole-plant test. 【Result】 The results showed that similar results were obtained by both of methods. In these two methods, the resistance factors of A. japonicus to haloxyfop-R-methyl, which were collected from Jurong in Jiangsu province, were 61.13 and 1331.68 respectively, which demonstrated the emergence of A. japonicus population resistant to haloxyfop-R-methyl in fields. The results of cross-resistance revealed that this resistant population of A. japonicus was also resistant to other AOPPs, in which the resistance level was: fluazifop-p-butyl＞quizalofop-p-ethyl＞fenoxaprop-p-ethyl. However, a relative low resistance level of this resistant population to sethoxydim was observed, which was a cyclohexanedione (CHD) herbicide sharing the same target with AOPPs. And the results obtained in laboratory were agreed with the real fact in fields.

Key words: haloxyfop-R-methyl, Alopecurus japonicus Steud., resistance