Significance of Weed Flora Identification and its Management on Bt Cotton (Gossypium hirsutum L.) Growing Tract of Tungabhadra Command Area

Aims: To identify the weed species in Bt cotton under Tunga-bhadra project command area and to study the effect of sequential application of pre- emergent (PE) and post- emergent herbicides (PoE) on weed growth and to know the efficiency of different weed control practices on weed species.

Study Design: The experiment was laid in RBD (Randomized Block Design).

Place and Duration of Study: The experiment was conducted at ICAR-Krishi Vigyan Kendra farm, UAS, Raichur situated in TBP command area during kharif season of 2018-19.

Methodology: The design was RBD with 11 treatments and replicated thrice. Gross plot size of the field was 7.2 m × 4.8 m and net plot size was 5.4 m ×3.6 m with spacing of 90 x 30 cm. The certified seeds of Jadoo Bt II Cotton with the test weight of 6.5 g was used for sowing. The crop duration was around 6 month

Results: Weed flora present in the Bt cotton field were identified and classified based on their morphology. It was divulged that; dicotyledonous weeds were dominant in cotton field. The sequential applications of metolachlor 50 % EC @ 1000 g a.i. ha-1 as PE fb pyrithiobac sodium 10 EC @ 125 g a.i. ha-1 as PoE @ 2-5 leaf stage of weeds fb Inter cultivation (IC) @ 60 DAS reported lower weed count and weed dry matter and reported the highest weed control efficiency (90.22 %) at harvest than the application of diuron 80 % WP as PE fb @ 1500 g a.i. and pendimethalin Pendimethalin 30 EC @ 1250 g a.i. ha-1 as PE followed by pyrithiobac sodium 10 EC @ 125 g a.i. ha-1 as PoE @ 2-5 leaf stage of weeds fb Inter cultivation (IC) @ 60 DAS.

Conclusion: Application of pre-emergent followed by post emergent herbicides control the early and later flush of weeds. It avoids the emergence of broad spectrum weed flushes and weed shift. Integrated herbicidal application along with intercultural operations was found better in keeping weeds under a threshold than following a single method.