Herbicidal performance of pretilachlor on rice (Oryza sativa L.) cv. IR-36 and lowland weed species as affected by rate, time of application and flooding
1987
Acse, J.L.
The response of rice (Oryza sativa L) cv. IR-36, Echinochloa colona, Echinochloa glabrescens, and Monochoria vaginalis to pretilachlor as affected by rate, time of pretilachlor application, and flooding time was investigated. Phytotoxicity rating on both the weed and the crop showed an increasing severity of injury as the rate was increased from 0.45, 0.60, 0.75 and 1.0 kg/ha. Recovery was decreased as the rate of pretilachlor applied was increased. In rice, application of 0.45 kg/ha induced slight phytotoxicity regardless of time of pretilachlor application; however, plants recovered rapidly. At 0.60 kg/ha, injury was greater and consequently recovery was slower. Severe phytotoxicity was observed at 0.75 kg/ha with some plants to recover. When treated with 1.0 kg/ha, however, it failed to develop well until maturity. Furthermore, plants treated with 0.75 and 1.0 kg/ha showed greater phytotoxicity when flooded later than when flooded right after application. Plants treated with 0.45 to 60 kg/ha were less affected. Reduction in yield parallelled with injury rating. The higher the rate of pretilachlor applied, the lower the yield. No yield was obtained when pretilachlor was applied at 1.0 kg/ha due to severe damage. In weeds, fresh and dry weights showed a decreasing trend with the rate of pretilachlor regardless of the time and stage of application. Echinochloa glabrescens showed the same response to pretilachlor as Echinochloa colona. Monochoria vaginalis was less sensitive to pretilachlor than the Echinochloa spp. Weed species used were most sensitive when treated at emergence and one day after emergence.
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