The biotypes of quinclorac-resistant barnyardgrass in Anxiang county and in Chede county of Hunan province were negative cross-resistance to butachlor with agar method and with litter cup method.

• 采用小杯法和琼脂法测得二氯喹啉酸抗性生物型湖南安乡县稗草和湖南常德市郊稗草对丁草胺出现了负交互抗性现象。