Efficacy of new generation herbicides for weed management in semi dry rice

A study was conducted during kharif season of 2014 to evaluate the weed control efficiency of low dose high efficiency new generation herbicides in semi dry rice in Kerala. The new herbicides evaluated were benzsulfuron methyl + pretilachlor @ 60 + 600 g a.i. ha -1 , pyrazosulfuron ethyl @ 25 g a.i. ha -1 along with post emergent herbicide azimsulfuron @ 30 g a.i. ha -1 . Results of the study revealed substantial reduction in weed population and biomass in all the herbicide treated plots compared to weedy check. Pre-emergent herbicide application followed by either hand weeding at 40 DAS or application of post emergent herbicides recorded higher weed control efficiency in comparison with hand weeding twice (20 and 40 DAS). Grain yield (4817.67 kg ha -1 ) and straw yield (7969.33 kg ha -1 ) were significantly higher on application of benzsulfuron methyl + pretilachlor followed by hand weeding at 40 DAS. Yield loss due to weeds was found to be 52.22 per cent and the most economically viable weed management practice was pre emergent application of pyrazosulfuron ethyl followed by azimsulfuron with a B: C ratio of 1.76, which was on par with pre emergent application of benzsulfuron methyl + pretilachlor followed by azimsulfuron @ 30 g a.i. ha -1 . Hence pre-emergence application of either benzsulfuron methyl + pretilachlor @ 60 + 600 g a.i. ha -1 or pyrazosulfuron ethyl @ 25 g a.i. ha -1 on the day after sowing followed by post emergence application of azimsulfuron @ 30 g a.i. ha -1 at 25 DAS could be recommended as the most effective weed management practice for semi dry rice.