Johnsongrass (Sorghum halepense) control in fallow sugarcane (Saccharum spp. hybrids) fields

Soil-and foliar-applied herbicide treatments were evaluated for the control of seedling johnsongrass in the interim between row formation and the planting of fallowed sugarcane fields approximately 90 d later. Soil-surface applications of metribuzin at 1,680 g ai/ha, pendimethalin plus atrazine each at 2,240 g ai/ha, terbacil at 1,680 g ai/ha, and sulfometuron at 35 and 70 g ai/ha and an incorporated application of trifluralin at 2,240 g ai/ha followed by a surface application of atrazine at 2,240 g/ha did not consistently control seedling johnsongrass until the crop was planted. Rhizome johnsongrass populations originating from seedling johnsongrass that escaped the fallow treatments were lowest in the newly planted crop when sulfometuron at 140 to 280 g/ha was applied to the soil surface and when glyphosate was applied POST at 2,240 g ai/ha, particularly as a sequential treatment alone or as a spot treatment at 2% by volume following applications of metribuzin, terbacil, and pendimethalin or trifluralin with atrazine. Sugarcane shoot populations in the fall after planting and sugar yields at the end of the crop's first growing season were highest where fallow treatments minimized johnsongrass development. These treatments also provided broad spectrum control of other seedling weeds, the residues of which influenced crop development.