The efficacy of imazethapyr in drill-seeded imidazolinone-resistant rice was evaluated in Louisiana in 2000 and 2001. Imazethapyr was applied preemergence (PRE), or no PRE, followed by a postemergence (POST) application of imazethapyr alone, or in a mixture with bensulfuron, bentazon plus aciflurofen, carfentrazone, halosulfuron, propanil plus molinate, triclopyr, or V-10029. Imazethapyr applied PRE followed by a POST application of imazethapyr controlled barnyardgrass equivalent to or higher than other treatments evaluated. Red rice control at 35 days after postemergence treatment (DAT) was 66 to 81% with imazethapyr applied PRE followed by any POST application, but a reduction in control was observed with a POST application of imazethapyr. Although alligatorweed control increased with POST applications, these treatments suggested only suppression. Hemp sesbania control never exceeded 10% with imazethapyr-only treatments and at 35 DAT, all POST applications, except bensulfuron, increased control above 84%. Rice yield increased with treatments receiving a PRE application of imazethapyr compared with no imazethapyr applied PRE.
Nomenclature: Acifluorfen; bensulfuron; bentazon; carfentrazone; halosulfuron; imazethapyr; molinate; propanil; V-10029, sodium 2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate; alligatorweed, Alternanthera philoxeroides (Mart.) Griseb. #3 ALRPH; barnyardgrass, Echinochloa crus-galli (L.) Beauv. # ECHCG; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex A.W. Hill # SEBEX; red rice, Oryza sativa L. # ORYSA; rice, Oryza sativa L. imidazolinone-resistant ‘93 AS-3510’ and ‘CL 121’.
Additional index words: Acetolactate synthase; Clearfield rice, herbicide mixtures.
Abbreviations: ALS, acetolactate synthase (EC 126.96.36.199); DAT, days after postemergence treatment; IR, imidazolinone-resistant; POST, postemergence; PPI, preplant incorporated; PRE, preemergence.