NDSU Extension Service Horticulturists Quack grass and bentgrass are undesirable perennial grasses that grow as weeds in many lawns. There is no herbicide you can use to kill these two grasses that does not kill the desirable lawn grasses. Bentgrass is shallow-rooted. You can remove patches of bentgrass by cutting the patch out with a hand sod cutter or shovel. Cut down one-inch deep.
Quack grass produces many underground stems almost impossible to remove by digging.
Broken pieces of stems left in the soil give rise to more quack grass plants. Glyphosate kills all grasses and most broadleaf plants. Apply glyphosate in May or September when the grasses are actively growing. Wait five to seven days to re-seed or sod the area. If you have further questions, contact your county office of the NDSU Extension Service for additional information on controlling quack grass and bentgrass.