Post-Emergence Control of Windmillgrass (<i>Chloris verticillata</i> Nutt.) Using Selected Herbicides

Abstract

Windmillgrass ( Chloris verticillata Nutt.) is spreading from native areas, becoming problematic in established turf in Missouri, and surrounding states. Limited information is available regarding post-emergence (POST) control options for turf. The objective of this research was to assess the visual and biomass response of windmillgrass to selected herbicides approved for use in turf. In one study, a greenhouse experiment was conducted with POST application of seven selected herbicides, including dimethylamine salt of quinclorac, fenoxaprop-P-ethyl, foramsulfuron, mesotrione, sulfentrazone, and topramezone in a tank-mixture with triclopyr, as well as a pre-packed product containing thiencarbazone-methyl, foramsulfuron, and halosulfuron-methyl. Under the same experimental conditions, five additional treatments, including mesotrione or topramezone applied at label-suggested rates alone or in combination with triclopyr, in addition to triclopyr alone, were applied to a second study on tillering windmillgrass. At 4 weeks after treatment (WAT), only fenoxaprop-p-ethyl consistently resulted in a complete control of windmillgrass. No measurable regrowth of plants was observed two weeks following the initial collection of windmillgrass aboveground biomass. In the second study, combinations of mesotrione and topramezone with triclopyr resulted in 100% visual injury of windmillgrass at 4 WAT; mesotrione and topramezone alone only resulted in up to 66% visual injury. Triclopyr alone resulted in 91% injury at 4 WAT. The greatest reduction of windmillgrass biomass and least amount of regrowth resulted from mesotrione and topramezone combinations with triclopyr. Control of windmillgrass is effective with fenoxaprop-P-ethyl alone, but use of a 4-Hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor such as mesotrione and topramezone should include the addition of triclopyr.