The effects of water management, timing and the rate of several herbicides on the growth of Murdannia keisak (Hassk.) Handel-Mazz

Murdannia keisak is a competitive rice weed found throughout the world. The aims of this study were to investigate the influence of different water managements on the growth of M. keisak under greenhouse conditions, and to assess the efficacy of common rice herbicides against it under field conditions. Three water management techniques were tested under greenhouse conditions: saturation, inter- mittent irrigation, and continuous flooding. The efficacy against M. keisak was evaluated in paddy fields during 2003e2005. In 2003, bispyribac-sodium was applied alone or in combination with triclopyr or metosulam at 20, 27, and 32 days after seeding (DAS). In 2004 and 2005, bispyribac-sodium was applied once (30 DAS), but at two application rates. Results for the three water treatments showed continuous flooding reduced M. keisak biomass most as confirmed by aboveground fresh weights. In the paddy field experiments, bispyribac-sodium also proved highly effective against M. keisak and was selective to rice with more than 90% efficacy. The addition of tryclopyr or metosulam to bispyribac-sodium failed to improve its herbicidal efficacy. Finally, the best M. keisak control at field condition was obtained with continuous flooding combined with bispyribac-sodium.