Most of the barnyard grass populations in Jiangxi, Heilongjiang and other 8 cities have developed resistance to Cyhalofop-butyl

 In order to determine the resistance of 56 Barnyard grass populations to Cyhalofop-butyl and Metamifop collected from 8 cities of Shanghai, Zhejiang, Jiangsu, Anhui, Hubei, Hunan, Jiangxi and Heilongjiang, The National Key Laboratory of Rice Biological Breeding of China National Rice Research Institute, GreenTech, and CAC Group, used indoor whole plant bioassay method to spray the stems and leaves of Barnyard grass at 3 ~ 4 leaf stages. The sensitivities of 56 barnyard grass populations to Cyhalofop-butyl and Metamifop were measured at 105 and 420g a.i./hm2. Two relatively sensitive populations and suspected resistant populations with less than 60% control efficiency at low dose were selected for resistance level determination.

Of the 56 Barnyard grass populations, 5 (8.93%) were sensitive to Cyhalofop-butyl and 26 (46.43%) were sensitive to Metamifop. There were 51 (91.07%) populations resistant to Cyhalofop-butyl and 30 (53.57%) populations resistant to Metamifop.

Five barnyard grass populations that were sensitive to Cyhalofop-butyl were also sensitive to Metamifop, and 30 barnyard grass populations that were resistant to Metamifop were also resistant to Cyhalofop-butyl. According to the researchers, Barnyard grass population collected from Shanghai, Zhejiang, Jiangsu, Anhui, Hubei, Hunan, Jiangxi and Heilongjiang paddy fields has developed different degrees of resistance to Cyhalofop-butyl, and the resistance frequency to Metamifop is lower than that of Cyhalofop-butyl,, and some barnyard grass population has cross-resistance to Cyhalofop-butyl and Metamifop.