Field studies were conducted in 1992 and 1993 to evaluate imazapic alone and in postemergence (POST) mixtures with atrazine or bentazon for weed control in imidazolinone-resistant corn treated with carbofuran. Nicosulfuron and nicosulfuron plus atrazine also were evaluated. Imazapic at 36 and 72 g ai/ha controlled large crabgrass 85 and 92%, respectively, which was equivalent to control obtained with nicosulfuron plus atrazine. Imazapic at the higher rate controlled large crabgrass better than nicosulfuron alone. Imazapic at 36 and 72 g/ha controlled Texas panicum 88 and 99%, respectively, and at the higher rate control was equivalent to that obtained with nicosulfuron alone or in mixture with atrazine. Imazapic plus bentazon POST controlled Texas panicum less than imazapic at the lower rate applied alone. Redroot pigweed was controlled 100% with all herbicide treatments. Imazapic at either rate alone or in tank mixture with bentazon or atrazine controlled prickly sida >99%, which was superior to control obtained with nicosulfuron or nicosulfuron plus atrazine. Smallflower, entireleaf, ivyleaf, pitted, and tall morningglories were controlled 96% or greater with all herbicide treatments except nicosulfuron alone. Sicklepod control was >88% with all imazapic treatments, whereas control from nicosulfuron alone was 72%. Corn yields were improved by the addition of POST herbicides with no differences among POST herbicide treatments.
Nomenclature: Atrazine; bentazon; carbofuran, 2,3-dihydro-2,2-dimethyl-7-benzofuranylmethylcarbamate; imazapic; nicosulfuron; entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. #3 IPOHE; large crabgrass, Digitaria sanguinalis L. # DIGSA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; redroot pigweed, Amaranthus retroflexus L. # AMARE; sicklepod, Senna obtusifolia Irwin and Barneby (L.) # CASOB; smallflower morningglory, Jacquemontia tamnifolia Griseb. # IAQTA; tall morningglory, Ipomoea purpurea (L.) Roth. # PHBPU; Texas panicum, Panicum texanum Buckl. # PANTE; corn, Zea mays L. ‘Pioneer 3343IR’.
Additional index words: Imidazolinone-resistant corn.
Abbreviations: ALS, acetolactate synthase (EC 22.214.171.124); IR, imidazolinone resistant; POST, postemergence.