Study On The Resistance Of Alopecurus Japonicus In Oilseed Rape Field

Alopecurus japonicus Steud.is a major weed of oilseed rape field, which is serious harm and difficult to control, especially in the middle and lower region of Yangtze River in China. One purpose of the research is to investigate the resistance level of Alopecurus japonicus Steud. from oilseed rape field in Jiangsu province to haloxyfop-R-methyl and its cross-resistance leve to other AOPP and CHD herbicides. The resistance level of 12 A. japonicus populations from 11 counties (cities) in Jiangsu province to haloxyfop-R-methyl and the cross-resistance level of some populations to other herbicides were assessed by seed bioassay. The toxicity determination of resistant A. japonicus populations to clethdim and haloxyfop-R-methyl and their different ratio was assessed by whole-plant test, and the field control test was conducted. The results summarized as follows:The results in resistance level experiments showed that the relative resistance factors of 2 populations to haloxyfop-R-methyl from Jurong were 76.03 and 61.18, and 3 papulations from Danyang, Gaochun and Liyang were 5.89,4.37 and 4.29. The most sensitive population was from Yixing, its relative resistance factor was 1.37. Resistance of some A. japonicus populations has occurred to haloxyfop-R-methyl.The cross-resistance test show that the resistant populations were also resistant to other AOPP herbicides, in which the resistance was in order of fluazifop-P-butyl quizalofop-P-ethyl> fenoxaprop-P-ethyl. However, the resistant populations were more sensitive to clethdim, which was a cyclohexanedione herbicide sharing the same target as AOPP herbicides.The results of indoor toxicity determination showed that when the ratio of active ingredients of clethdim and haloxyfop-R-methyl were 0.25:1,0.5:1,1:1,1.5:1,2:1,3:1 and 4:1, their co-toxicity coefficient were 86.05,87.13,83.55,80.50,111.31,99.39,118.22, respectively. It showed that the inter-toxicity of clethdim and haloxyfop-R-methyl was additive. The result of field control test showed that the mixture of 24% clethdim EC and 10.8% haloxyfop-R-methyl EC applied at the dosages of 375 mL plus 450mL,300mL plus 225mL and 375mL plus 225mL per hectare in which the mixture ratios of active ingredients were 1.9:1,3.0:1,3.7:1. Their stem control effect were 94.34%,91.79% and 94.75% and the fresh weight effect were 97.82%,85.21% and 97.15% after 60 days, respectively.