Weed control in wheat with pyroxasulfone and its combinations with other herbicides

Field and pot investigations were conducted to determine the effectiveness of pyroxasulfone alone and its combinations with other herbicides against diverse weed flora of wheat (Triticum aestivum L.) including multiple herbicide-resistant (MHR) littleseed canarygrass (Phalaris minor Retz.). Applications of pyroxasulfone 100-127.5 g/ha as pre-emergence (PE) or early post-emergence (EPOE) @ 63.75 g/ha at 21-23 days after sowing (1 day before irrigation) were highly effective for control of grass weeds namely P. minor and wild oat (Avena ludoviciana Dur.). It was poor for control of broad-leaved weeds (Medicago denticulata Willd. and Rumex dentatus L.). However, pyroxasulfone in tank-mix combination with metsulfuron 4 g/ha, triasulfuron 20 g/ha, and pyroxsulam 18 g/ha effectively controlled (96.5%-99.8%) the diverse weed flora and improved the wheat grain yield (69.5%-285.9%) over untreated weedy control. Also, the pre-mix of pyroxasulfone + pendimethalin applied as PE was superior to either of these applied alone for weed control and grain yield. Pyroxasulfone 100-127.5 g/ha had yield gain of 119.6%-125.4% and 10.1%-26% over untreated control and pendimethalin 800-1250 g/ha, respectively. In pot studies, straw burnt ash drastically reduced the pyroxasulfone efficacy against P. minor and A. ludoviciana. Pyroxasulfone was also effective in pot studies for control of MHR P. minor having resistance against acetyl-coA carboxylase (ACCase), acetolactate synthase (ALS), and photosynthesis at the photosystem-II site-A (PS-II) inhibitor herbicides (clodinafop, sulfosulfuron, and isoproturon, respectively). The studies indicate that pyroxasulfone as PE or EPOE can be an alternative grass weed control herbicide in wheat in particular for the control of MHR P. minor.