Interaction between timings and doses of quindorac in rice

Abstract

SummaryQuinclorac (3,7‐dichloro‐8‐quinolinecarboxylic acid) is a new herbicide in United States rice production. Field studies were conducted in 1990 and 1991 in Mississippi to determine the influence of application timings and rates on weed control efficacy and rice yield. Control of Echinochloa crus‐galli (L.) Beauv. (barnyard‐grass), Sesbania exaltata (Raf.) Rydb. ex A. W. Hill (hemp sesbania) and Ipomoea wrightii Gray (palmleaf morning glory) were greatest with early post‐emergence application. Efficacy of pre‐emergence application depends strongly on soil moisture, with significantly reduced weed control resulting when applied to dry soil. Weed control with pre‐emergence application to moist soil was comparable with early post‐emergence application at higher rates of quinclorac. Pre‐plant and incorporated quinclorac controlled weeds effectively. Control of E. crus‐galli, S. exaltata and I. wrightii ranged from 73 to 99%, 75 to 99%, and 92 to 99% at 28 days after treatment, respectively. Rice yield generally reflected weed control. No rice injury was observed for any treatment. Results indicate that early post‐emergence application of quinclorac is the best time for using reduced rates and field conditions at application should be considered with these rates pre‐emergence.