Field studies were conducted to determine the feasibility of using imazethapyr applied preemergence (PRE) and postemergence (POST) for weed control in sericea lespedeza. In the POST experiment, imazethapyr was applied at 0, 71, 142, and 213 g ai/ha to mature, recently mowed stands of sericea lespedeza. Regardless of rate, yellow nutsedge and cutleaf groundcherry control at 2 mo after treatment, as determined by weed foliage biomass relative to the nontreated plants, was 90 and 80%, respectively. Sericea lespedeza forage yield (weeds removed) was not reduced by POST-applied imazethapyr even at 213 g/ha. The same imazethapyr rates were used with newly seeded sericea lespedeza in the PRE-applied experiment. Imazethapyr at 71 g/ha provided at least 78% control of large crabgrass, stinkgrass, yellow nutsedge, sicklepod, and cutleaf groundcherry as well as maximum sericea lespedeza performance, as indicated by seedling height, weight, and stand count. Results indicated that imazethapyr can be used for either PRE- or POST-applied weed control in sericea lespedeza. However, margin of safety is greater with imazethapyr applied POST to mature stands than with PRE applications to germinating seeds.
Nomenclature: Imazethapyr; cutleaf groundcherry, Physalis angulata L. #3 PHYAN; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; sericea lespedeza, Lespedeza cuneata (Dumont) G. Don.; sicklepod, Senna obtusifolia (L.) Irwin and Barnaby # CASOB; stinkgrass, Eragrostis cilianensis (All.) E. Mosher # ERACN; yellow nutsedge, Cyperus esculentus L. # CYPES.
Additional index words: Forage, legume.
Abbreviations: POST, postemergence; PRE, preemergence.