Windmill grass is difficult to control with herbicides. To potentially improve control, use high water rates and a nozzle type designed for broad coverage to ensure herbicide covers all seedlings (or the entire plant tuft if spraying mature plants). Try to apply herbicides 7-21 days after summer rainfall, to target young plants. If plants are older, or dry and stressed at the time of spraying, use higher rates of herbicide.
There are few registered herbicide options for windmill grass. Under Western Australian legislation, a herbicide can be used against a weed that is not on the label, as long as the herbicide is registered for use in the agricultural system and/or crop in question. However, if a weed species is not on the herbicide label, then the herbicide may not effectively kill that species.
Registered herbicides for windmill grass include:
- Touchdown Hi Tech® (glyphosate as potassium salt 500g active ingredient per litre (a.i./L)) can be used for non-selective control.
- butroxydim (for example, Factor®) can be applied to legume crops in the small seedling stage.