SULFONYLUREA RESISTANT WEEDS OCCURRED IN RICE FIELDS IN SOUTH-WESTERN REGION OF KOREA AND THEIR RESPONSE TO SEVERAL OTHER HERBICIDES

摘要

A survey to ascertain the relative occurrence of sulfonylurea (SU) resistant weeds was conducted in paddy fields of the south-western region, Korea in 2000. These fields have been used for monoculture of rice (Oryza sativa L.) poduction with wet direct-seeded rice and infant seedling culture with machine transplanting, and have been treated with sulfonylurea-included herbicide mixture for several years. The resistant biotypes of Monochoria vaginalis (M. vaginalis) and Lindernia attenuata (L. attenuata) to bensulfuron-methyl (BSM) were newly identified in 8 sites and 2 sites of sampling areas, respectively. The survival rates of resistant biotypes of M. vaginalis and L. attenuata collected from these sites were ranging from 44 to 80% and from 71 to 100% even at 5 times higher rate of the recommended dose of BSM, respectively. However, the susceptible biotypes of two species were completely controlled at the recommended dose. GR_(50) values (concentration of BSM for inhibiting fresh weight of weeds by 50%) of the resistant M. vaginalis and L. attenuata sampled from south-western region of Korea were 65 to 128 times and 114 to 140 times respectively higher, than those of the susceptible biotypes. Three SU resistant biotypes of Monochoria korsakowii, M. vaginalis and L. attenuata as of 2000 have confirmed in paddy fields in Korea. Butachlor, pyrazolate, pretilachlor and thiobencarb controlled the SU resistant biotypes of M korsakowii, M. vaginalis and L. attenuata effectively without serious rice injury in the pot experiment under wet-seeded rice and infant seedling culture with machine transplanting culture.