Herbicides for Nutsedge

Pre-Emergent Herbicides

• Pre-emergent herbicides help to control weeds by inhibiting the germination of weed seeds before the plants get a chance to grow and get established. Pre-emergent herbicides for nutsedge include dichlobenil, dimethenamid-P and metochlor, as recommended by the University of California Extension. However, none of these, or any other pre-emergent herbicide, is effective for purple nutsedge control.

Application Suggestions

• The recommended pre-emergent chemicals work only for controlling yellow nutsedge. Do not use any pre-emergent nutsedge herbicide on nutsedge growing in turf grass. Reapply herbicides for long-term control. Products containing dimethenamid-P and metolachlor are relatively safer to use around ornamental plantings than dichlobenil. However, the chemicals are not available to homeowners and need to be applied by professional applicators.

Post-Emergent Herbicides

• Post-emergent herbicides control weeds that have already started to grow. Nonselective post-emergent herbicides affect all plants indiscriminately and include glyphosate and glyphosate with nonaoic. The selective post-emergent herbicides for nutsedge that work exclusively on nutsedge include MSMA and halosulfuron. Trifloxysulfuron-sodium and sulfosulfuron also are post-emergent nutsedge control strategies but are available only to professional applicators.

Application Suggestions

• Glyphosate works best on very young, actively growing weeds and has a low rate of efficacy once the tubers get mature. Apply glyphosate during warm and sunny weather, and avoid using on windy days to minimize drift. MSMA and halosulfuron work best at the fifth leaf stage. When applied later than this stage, only the above-ground portions of the weed are affected. The tubers remain unaffected. MSMA works better on yellow nutsedge than purple. Read all labels carefully before use, as certain formulations may not be recommended for use on turf grasses.