Weed control efficacy and plant residue determination of oxyfluorfen applied preemergence in transplanted broccoli

Field studies were conducted to evaluate the weed control efficacy of the herbicide oxyfluorfen applied preemergence at rates of 0.28, 0.42, 0.56 and 1.12 kg ai/ha in spring and fall trans-planted broccoli (Brassica oleracea var. italica L. cv. 'Premium Crop'). Oxyfluorfen at all rates evaluated provided excellent control (90-100%) of redroot pigweed (Amaranthus retroflexus L.), common purslane (Portulaca oleracea L.), turnip (Brassica rapa), goosegrass [Eleusine indica (L.) Gaertn.], and large crabgrass [Diqitaria sanquinalis (L.) Scop.]. Oxyfluorfen at rates of 0.56 kg/ha or greater was needed for commercially acceptable control of the annual grass weeds fall panicum (Panicum dichotomiflorum Michx.), giant foxtail (Setaria faberi Herrm.), and Italian ryegrass (Lolium multiflorum Lam.). In one test, crop phytotoxicity and subsequent reduced yields resulted from oxyfluorfen at the highest rate. In all other tests some early crop phytotoxicity was observed among oxyfluorfen treat-ments, but no reduction in yield occurred. Gas-liquid chromatographic analysis of oxyfluorfen residues was performed on head tissue of plants grown on soil that received the highest rate (1.12 kg/ha) of the herbicide. Neither the parent compound nor any of its metabolites were detected in broccoli head tissue using the accepted analytical method which is sensitive to 0.01 ppm.