Field experiments were conducted in 2003 and 2004 to determine the tolerance of direct-seeded leafy turnip greens, mustard greens, kale, and collard to selected preemergence and postemergence herbicides and to determine the efficacy of these herbicides against weeds that are common to the southeastern coastal plains of the United States. Pendimethalin applied preemergence controlled large crabgrass, goosegrass, carpetweed, and common purslane, but it injured turnip greens, mustard greens, kale, and collard. Dimethenamid at 0.31 and 0.63 kg ai/ha controlled large crabgrass and goosegrass but did not control hairy nightshade or common purslane at the lower rate. In 2003, dimethenamid at 0.63 kg/ha injured mustard greens, kale, and collard more than 40%. S-metolachlor applied preemergence at 0.45 kg ai/ha controlled large crabgrass, goosegrass, hairy nightshade, and common purslane while causing little or no injury to turnip greens, mustard greens, kale, and collard. Clopyralid at 0.10 kg ai/ha controlled common lambsquarters 76 to 95% and hairy nightshade 93% but did not control carpetweed, common purslane, large crabgrass, and goosegrass. Turnip greens, mustard greens, kale, and collard generally were tolerant of clopyralid, but mustard was injured 29% in 2003. Phenmedipham alone or in combination with desmedipham injured mustard greens 54 to 82% in 2003 and failed to control weeds. Of the herbicides evaluated, S-metolachlor provides the best potential to improve weed control in direct-seeded leafy greens in the southeastern United States.
Nomenclature: Clopyralid; desmedipham; dimethenamid; pendimethalin; phenmedipham; S-metolachlor; carpetweed, Mollugo verticillata L. #3 MOLVE; collard, Brassica oleracea L. var. acephala DC ‘Top Bunch’; common lambsquarters, Chenopodium album L. # CHEAL; common purslane, Portulaca oleracea L. # POROL; goosegrass, Eleusine indica (L.) Gaertn. # ELEIN; hairy nightshade, Solanum sarrachoides Sendtner # SOLSA; kale, Brassica oleracea var. acephala ‘Blue Knight’; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; leafy turnip greens, Brassica rapa L. Alamo'; mustard greens, Brassica juncea (L.) Czernj. & J. M. Coulter var. crispifolia L. H. Bailey ‘Southern Curled Giant’.
Additional index words: Herbicide tolerance, weed control.
Abbreviations: WAP, weeks after planting; WAT, weeks after treatment.