Glyphosate is a broad-spectrum systemic herbicide that will attack and kill quackgrass. For this herbicide to work well the grass should be actively growing and green and is particularly effective for pre-planting clearing of soil of post-emergent quackgrass. Use glyphosate carefully around other plants, as this herbicide is very non-selective and can kill desirable plants on contact. If necessary, use a paintbrush to brush on glyphosate in garden settings for a greater level of control. Multiple applications may be necessary, as quackgrass may grow back from unaffected rhizomes after glyphosate degrades.
Fluarifop is a selective herbicide that can be used more safely on quackgrass, especially around non-fruit bearing perennial plants, vines, shrubs and trees and certain vegetable crops, according to the University of Minnesota. This herbicide is best applied during a dry period on young quackgrass plants. Multiple applications may be required to eradicate the grass completely.
For treating quackgrass in alfalfa and other legume plantings, sethoxydim may be effective. This herbicide should be applied when quackgrass is young and still under 8 inches tall. Applications should not be performed within seven days of livestock grazing in a treated area or harvesting forage, or within 20 days of cutting hay from the area. Secondary treatment may be required for full control.
Sulfosufuron is a selective turf herbicide rated for the control of several perennial weeds, including quackgrass in lawns and plantings of certain crops, such as wheat or switchgrass. The herbicide is applied to post-emergent quackgrass in the fall and spring to suppress or control the weed, although it usually is not completely eradicated. Typically, sulfosulfuron provides 80 to 90 percent control.