Effect of Various weedicides on weed control, yield and economics in Bt cotton (Gossypium hirsutum L.) International Journal of Tropical Agriculture 1091 INTERNATIONAL JOURNAL OF TROPICAL AGRICULTURE ISSN : 0254-8755 available at http: www. serialsjournals. com © Serials Publications Pvt. Ltd. Volume 36 • Number 4 • 2018 Effect of Various weedicides on weed control, yield and economics in Bt cotton (Gossypium hirsutum L.) A. D. Pandagale * , K. S. Baig, S. S. Rathod, Kadam G. L. and Namade T. B. Cotton Research Station, Nanded (M.S., India) * E-mail: arvindpandagale@yahoo.co.in Abstract: A field study was undertakento evaluate efficacy of PE and PoE weedicides in Bt cotton during 2012-13 to 2014-15 under rainfed condition at Cotton Research Station, Nanded (M.S., India) for three years in kharif season.The trial was laid out in randomized block design having eight treatmentswith three replications. Weedicides, Pendimethalin (PE), Quizalofop ethyl (PoE), Pyrithiobac sodium (PoE) and Glyphosate (PoE – directed spray) were evaluated as single or in combination along with weed free check and weedy check.The weedicide treatments recorded increase in seed cotton yield to the tune of 75.52 to 150.44 per cent as compared to weedy check. Weeds had reduced seed cotton yield by 60.58 per cent when they are not controlled. Pre-emerngence application of Pendimethalin had contolled weeds in initial period only. Glyphosate 41 SL @ 1.0 kg a.i. ha -1 as directed spray at 45 DAS recorded highest weed control efficiency (WCE) of monocot as well as dicot weeds at 9 WAS and at harvest. The tank mix application of Pyrithiobac sodium 10 EC @ 62.5 g a.i. ha -1 + Quizalofop ethyl 5 EC @ 50 g a.i. ha - 1 followed by one hoeing at 45 DAS treatment was highest selective weedicide treatment to record WCE. The weed free check recorded highest seed cotton yield (1698 Kg ha -1 ) and was on par with treatments Glyphosate (1572 Kg ha -1 ) and tank mix Pyrithiobac sodium + Quizalofop ethyl fb one hoeing (1570 Kg ha -1 ).Among weedicides, Glyphosate was the most efficient treatment in terms of yield and weed dry matter. Treatment Efficiency Index for monocot weeds was lower in treatments having. Among selective weedicides, Quizalofop ethyl (PoE) weedicide was found effective against monocot weeds whereas for dicot weeds, Pyrithioback sodium (PoE) application was found effective.Directed spray of Glyphosate at 45 DAS was profitable in terms of highest NMR (Rs. 34,549/- ha -1 ) and Pyrithiobac sodium + Quizalofop ethyl fb one hoeing (NMR – Rs. 31,493/- ha -1 and B:C ratio – 1.83) was remunerative among selective weedicides. Keywords: Bt cotton, economics, seed cotton yield, weedicide, weed control efficiency.