Current Status of Rice Herbicide Use in the Tropics
JIRCAS international symposium series
Chemical weed control for rice in the tropics began with the use of the chlorophenoxy herbicides in the 1950s. MCPA and 2, 4-D were used routinely in transplanted wetland rice for controlling broadleaved weeds and sedges. Propanil was introduced subsequently in the mid-1960s for postemergence control of annual grasses such as Echinochloa crus-galli and Leptochloa chinensis. Over the past decades, intensive research has led to the discovery, development and marketing of a wide spectrum of rice herbicides in the tropics. Those used include bensulfuron methyl, pyrazosulfuron-ethyl, cinosulfuron, bentazon, butachlor, piperophos thiobencarb, quinclorac, fenoxaprop-ethyl, molinate, pretilachlor oxadiazon, piperophos, dimethametryn, bifenox, pendimethalin and oxyfluorfen. The switch from transplanted to·direct-seeded rice in recent years has triggered more weed infestation in tropical rice. Herbicides·are the only logical alternative for weed control in direct seeding culture; however, continuous herbicide application causes a distinct shift in the weed flora from annuals to perennials. Repeated use of the same herbicide also results in the development of herbicide-tolerant strains or resistant biotypes. Increasing herbicide usage has created concern regarding hazards to rice farmers' health. In the next decade, rice herbicide use in the tropics is expected to expand further because of increasing popularity of direct-seeded rice in the· irrigated areas. It is therefore imperative to evaluate the impact of herbicides from the perspective of social implication such as potential environmental and health costs. Experiences of integrated weed management in Malaysia reveal that it is possible to reduce herbicide application through farmers' education with emphasis on proper cultural practices and good water management.
|著者キーワード||herbicidesweed shiftdirect seeding|
|公開者||Japan International Research Center for Agricultural Sciences|