Abstract
Occurrence of a biotype of Monochoria vaginalis Presl resistant to sulfornylurea herbicides was confirmed in paddy fields of 15 cities and counties in Chungnam region. Efficacy of sulfonylurea herbicides such as azimsulfuron, imazosulfuron and cyclosulfamuron to resistant Monochoria vaginalis was generally poor. The resistant biotype of M. vaginalis to ALS inhibiting herbicides was controlled by oxadiazon, oxadiargyl, pyrazosulfuron-ethyl plus pyrazolate plus simetryn, and fentrazamide followed by MCPA plus bentazon. Oxadiazon or oxadiargyl fb any sulfonylurea herbicides controlled M. vaginalis and perennial paddy weeds. All sequential application treatments except pyriftalid plus cinosulfuron fb bentazon controlled M. vaginalis 60 days after treatments. Pyrazosulfuron-ethyl plus pyrazolate plus simetryn fb cyclosulfamuron plus fentrazamide and oxadiazon fb pyrazosulfuron-ethyl plus fentrazamide were most effective to control annual weeds and perennial weed. Rice yield was 5.19~5.29 ton $ha^{-1}$ in pyrazosulfuron- ethyl plus fentrazamide and 5.35~5.62 ton $ha^{-1}$ in all sequential application treatments except pyriftalid plus cinosulfuron followed by bentazon