Bio-efficacy of pre- and post-emergence herbicides alone and in combination against herbicide resistant Phalaris minor in wheat (Triticum aestivum L.)

Abstract

Abstract Herbicide resistance in littleseed canary grass (Phalaris minor Retz.) in wheat is a major concern along with crop residue management, which puts the question mark on sustainable growth of rice-wheat (R-W) system in north-western Indo-Gangetic Plains in long path. Crop rotation with integrated weed management is the best way to address or avert the herbicide resistance issues but due to cereal economics, cost and time bound obligations in dealing with weeds, farmers are still continuing with mono-cropping and relying on chemical weed control. Researchers were forced to think about herbicide rotation, by adopting the sequential or tank-mix applications of pre- and post-emergence herbicides. To evaluate the bio-efficacy of pre- and post-emergence herbicides alone and in combination against Phalaris minor in wheat, a field experiment with 18 treatments was conducted on CCSHAU Regional Research Station, Karnal during the rabi seasons of 2016-17 and 2017-18. Total seven herbicides three as pre-emergnce (pendimethalin, metribuzin and pyroxasulfone) and four as post-emergence (clodinafop, sulfosulfuron, pinoxaden and mesosulfuron + iodosulfuron RM) along with hand weeding were evaluated as alone or in combination as sequential or tank mix. Contrary to farmers’ fields, recommended herbicides are still providing good control of P. minor at Research Farm, however their efficacy is also getting down. Yield loss could be restored by using already recommended herbicides in combination with pre-emergence herbicide pendimethalin or metribuzin. Overall, metribuzin (PRE) followed by sulfosulfuron (POE) (175 fb 25 g ha− 1) was found to be the best treatment in terms of weed control efficiency (WCE), grain yield, gross return, net return and B-C ratio. Mesosulfuron + iodosulfuron (ready-mix) alone and in combination with pre-emergence herbicides (metribuzin) also performed well against weeds (P. minor as well as broadleaf) but its consistency was poor. Pyroxasulfone was best herbicide against P. minor with complete control, but was not found that effective against broadleaf weeds mainly Melilotus spp. and also caused crop phyto-toxicity at 128 g ha− 1 but not that much pronounced at 105 g ha− 1.