Control of herbicide resistant Echinochloa crusgalli indirect-seeded rice crops.
Barnyardgrass (Echinochola crusgalli) is one of the more problematic grass weeds in Chinese rice paddies. Continuous application of the herbicide quinclorac since 1990 has resulted in barnyard grass developing resistance to quinclorac. The efficacy of six herbicides; penoxsulam, bispyribac-sodium, pyribenzoxim, flucetosulfuron, metamifop and cyhalofop-butyl for controlling resistant barnyardgrass was determined using pot and field based experiments. The pot trial showed that all six herbicides had good biological activity against quinclorac resistant barnyardgrass. The field trial revealed that 2.5% penoxsulam OD and 10% metamifop EC, applied at 22.5 g/ha and 120 g/ha respectively produced control efficacies of more than 95.0% 20 and 40 d after application. The control efficacy of 10% bispyribac-sodium SC (30 g/ha) was greater than 90.0% while the efficacy of 5% pyribenzoxim EC (40 g/ha) was greater than 85.0% after 20 and 40 d. However 10% cyhalofopbutyl EC (90 g/ha) and 10% flucetosulfuron WG resulted in less than 85.0% control efficacy. The results indicate that penoxsulam and bispyribac-sodium effectively controlled barnyardgrass resistant to quinclorac.