Field experiments were conducted in 2004 and 2005 to determine the tolerance of direct-seeded green onion to selected herbicides applied before or after green onion emergence. Preemergence herbicides included S-metolachlor, pendimethalin, dimethenamid, quinclorac, pronamide, ethofumesate, and DCPA, a registered standard. Herbicide applied to two- to three-leaf green onion included glyphosate, trifloxysulfuron, flumioxazin, phenmedipham, ethalfluralin, pendimethalin, S-metolachlor, and oxyfluorfen. Plots were cultivated and hand weeded to minimize negative effects of weed interference on the crop. All herbicides applied at seeding, excluding DCPA, caused excessive injury (>25%) to green onion in at least 1 of 2 years. Oxyfluorfen, ethalfluralin, or S-metolachlor applied after crop emergence caused less than 10% injury in both years to green onion. Green onion yields following treatment with oxyfluorfen, ethalfluralin, or S-metolachlor were equivalent to the nontreated control. All other herbicides applied after crop emergence resulted in height, density, or yield reductions relative to a nontreated control in at least 1 of 2 years.

Nomenclature: DCPA, dimethenamid, ethalfluralin, ethofumesate, flumioxazin, glyphosate, oxyfluorfen, pendimethalin, phenmedipham, pronamide, quinclorac, S-metolachlor, trifloxysulfuron, green onion, Allium cepa L. ‘White Spear 85’