Imazethapyr applied to the soil at 0, 35, 53, 70, 87, 105, and 140 g ai/ha followed by (fb) early-postemergence (EPOST) or late-postemergence (LPOST) applications at 140, 105, 87, 70, 53, 35, and 0 g ai/ha, respectively, was evaluated for weed control, crop tolerance, and grain yield in imidazolinone-tolerant rice. In drill- and water-seeded rice, imazethapyr effectively controlled barnyardgrass 91 to 97% with a soil fb EPOST or LPOST application except when applied at 105 fb 35 g/ha EPOST at 49 d after late-postemergence treatment. Rice yields were 5,920 and 3,920 kg/ ha in the drill-seeded study with a single application of imazethapyr at 140 g/ha EPOST in 2000 and 2001, respectively. These yields were greater than or equal to those from treatments with two imazethapyr applications.
Nomenclature: Imazethapyr; barnyardgrass, Echinochloa crus-galli (L.) Beauv #3 ECHCG; rice, Oryza sativa L. ‘93 AS-3510’, ‘CL 141’.
Additional index words: Acetolactate synthase, ALS, Clearfield rice.
Abbreviations: DAT, days after late-postemergence treatment; EPOST, early postemergence; fb, followed by; IT, imidazolinone tolerant; LPOST, late postemergence; POST, postemergence; PPI, preplant incorporated; PRE, preemergence; SURF, surface.
