Bio-efficacy of Herbicides with Different Water Volumes and Spray Timing under Zero Tillage Rice Residue Retention Scenario against Phalaris minor in Wheat

Background: Continuous use of the similar modes of action-based herbicides leads to the development of herbicide resistance in wheat-associated weeds in north-west India. Accelerated development of multiple resistance against most of the available post-emergence herbicides emphasize the use of pre-emergence herbicides. But, the efficacy of pre-emergence herbicide is a matter of concern as surface retained stubbles and/or straw alter herbicide efficacy associated with a direct interception of herbicide. Methods: A field study was conducted for two rabi seasons (2018-19 and 2019-20) to optimize spray volume and time of application for improving the bio-efficacy of pre-emergence herbicides under zero tillage full rice residue scenario. The herbicidal treatments (g/ha) included pendimethalin + pyroxasulfone (1000.0+127.5) as pre-emergence (PE), pyroxasulfone (127.5) as PE, pyroxasulfone (127.5) as early post emergence (EPoE), aclonifen+diflufenican (1002+200) EPoE, halauxifen methyl+ fluroxypyr (7.3+233.4) as EPoE, flumioxazin (100) as PE with two different water volumes 500 and 1000 liter/ha along with pendimethalin fb pinoxaden (1500+50) in 500 l/ha water volume, pendimethalin (1500) as PE in 375 l/ha water volume, weed free and weedy check. Results: The present study showed that pendimethalin + pyroxasulfone as PE with a higher spray volume of 1000 l/ha and alone application of pyroxasulfone as EPoE produced similar Phalaris minor control as with pendimethalin fb pinoxaden (PE fb Post) under full rice residue scenario in zero-till wheat.