Integrated management of rock bulrush (Schoenoplectus juncoides) in wet seeded rice
Field experiment was conducted at the College of Agriculture, Vellayani during Rabi 2017to formulate anintegrated weed management strategy for managementofrock bulrush (Schoenoplectusjuncoides), an emerging sedge weed in the lowland paddy fields of Kerala. The treatments comprised of pre-emergenceherbicide,bensulfuron methyl + pretilachlor 60+600 g ha-1 at 4-7 DAS;early post emergent herbicides penoxsulam 22.5 g ha-1, ethoxysulfuron 15 g ha-1,carfentrazone-ethyl 20 g ha-1each at 15 DAS;and post emergent herbicides metsulfuron- methyl+ chlorimuron-ethyl 4 g ha-1, 2, 4-D sodium salt 1 kg ha-1each at 20 DAS and all herbicides were followed by (fb)hand weeding (HW)at 40 DAS. Ethoxysulfuron @ 15 g ha-1 at 15 DAS fb HW at 35- 40 DAS (T3) was significantly superior with respect to productive tillers m-2, number of grains panicle-1 and number of filled grains panicle-1. Grain yield (5750 kg ha-1) obtained from the plots treated with ethoxysulfuron 15 g ha-1 at 15 DAS fb HW was higher and on a par with penoxsulam @ 22.5 g ha-1 at 15 DAS fb HW (5500 kg ha-1). Herbicides were effective in managing growth of bulrush during initial stages and the efficacy improved with a follow up HW at 35-40 DAS.Hand weeded plots (at 20 and 40 DAS)recorded lesser number of panicles m-2, grains panicle-1 and filled grains panicle-1compared to T3 as Schoenoplectusjuncoides escaped hand weeding due to its needle like leaf morphology that made itsidentification difficult during initial stages (20 DAS)in the cropped fields. The study revealed that unchecked weed growth in wet seeded paddy with predominance of Schoenoplectusjuncoides could cause a reduction of 81% in net income (Rs 19,264 ha-1) compared to the most economical weed management practice.