Effect of dose and spray volume on early-season broadleaved weed control in Allium using herbicides

Field studies were conducted near Oakes, Absaraka, and Carrington, North Dakota to determine if bromoxynil and oxyfluorfen applied post-emergence at reduced doses and spray volumes to one-leaf onion would provide effective early-season broadleaved weed control without significant crop injury. Oxyfluorfen generally provided more effective early-season broadleaved weed control than bromoxynil when applied at reduced spray volumes and doses. Onion injury 1 week after treatment (WAT) was more severe with oxyfluorfen than bromoxynil applied post-emergence, but was not visible 3 WAT. Large-grade and total onion yields at Absaraka, where broadleaved weed pressure was the least, were similar in all treatments except the untreated check. At Carrington and Oakes, where broadleaved weed pressure was much greater, no treatments had large-grade or total onion yields similar to the hand-weeded check. However, large-grade and total yields from onion treated with reduced doses of bromoxynil or oxyfluorfen, regardless of the spray volume, were similar to those treated with almost a four-fold increase in herbicide dose, suggesting that a reduced bromoxynil or oxyfluorfen dose at lower spray volumes to one-leaf onion may provide sufficient early-season Chenopodium album and Amaranthus retroflexus control so that post-emergence applications of bromoxynil plus oxyfluorfen to larger onion provide more effective broadleaved weed control.