Fenoxaprop for Postemergence Barnyardgrass (Echinochloa crus-galli) Control in Rice (Oryza sativa)

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Abstract
The ethyl ester of fenoxaprop {(±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy] phenoxy] propanoic acid} was applied to rice (Oryza sativa L.) that was heavily infested with barnyardgrass [Echinochloa crus-galli (L.) Beauv. # ECHCG] during a 3-yr study. Applications were made to two- to three-leaf, three- to four-leaf, five- to six-leaf, or tillering barnyardgrass. Barnyardgrass control at 9 weeks after final treatment was greater than 90% for all growth stages except the 0.1 kg ai/ha rate applied to three- to four-leaf barnyardgrass in 1983. In 1984, the sequential application of fenoxaprop made at the three- to four-leaf stage controlled more than 95% when rated at 9 weeks. Rates of 0.17 and 0.2 kg ai/ha and the sequential treatment of 0.1 kg ai/ha followed by 0.1 kg ai/ha 7 to 10 days later controlled greater than 90% at 9 weeks when applied to three- to four- and five- to six-leaf barnyardgrass in 1985. In general, barnyardgrass was controlled by fenoxaprop rates greater than 0.1 kg ai/ha when applied to any growth stage evaluated up through the five- to six-leaf stage. However, acceptable control of tillering barnyardgrass was achieved in only 1 of 3 years. Yields were increased due to barnyardgrass control all years with all treatments except those applied at tillering. However, control was sufficient to increase yields over that of the check for all tillering treatments except the 0.1 kg ai/ha rate in 1984 and 1985 and the 0.17 kg ai/ha treatment in 1985.