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New Zealand Plant Protection 63 (2010): 66-71

Herbicide efficacy on three annual grass weeds in soils with different cropping histories

A. Rahman and T.K. James


The efficacy of several pre-emergence herbicides on barnyard grass (Echinochloa crus-galli), smooth witchgrass (Panicum dichotomiflorum) and yellow bristle grass (Setaria pumila) was investigated in different soils in pot experiments. These soils were collected from the top 10 cm of seven maize fields with different cropping histories. The herbicides used were dimethanamid, alachlor, metolachlor, two formulations of acetochlor and proprietary mixes of acetochlor with atrazine or metribuzin. Plastic pots filled with soil were seeded with 10 seeds of individual grass species, and herbicide treatments were then applied with a precision pot sprayer. A further 10 seeds of the same grass species were sown at 2-weekly intervals for 8 weeks to test the duration of residual weed control. The number of emerged seedlings was counted in each pot at 2 weeks after each planting. Metolachlor was the most effective chemical for controlling E. crus-galli and P. dichotomiflorum. For S. pumila, similar levels of control were achieved by all treatments evaluated. Generally, all the herbicides were less effective in soils with a long history of maize growing where up to three times more seedlings emerged than in soils with only 1-2 years of maize cropping.

Keywords: Echinochloa crus-galli, Panicum dichotomiflorum, Setaria pumila, grass weeds, chemical control, herbicide efficacy, enhanced degradation, maize.

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