Nike from Michigan writes
You will want to wait until the newly germinated turf has been mowed two times or four weeks after emergence (whichever is longer) before making a postemergence application with Tenacity Herbicide to the new cool season turf. For the most effective Bentgrass control, you will need to reapply Tenacity Herbicide at two to three-week intervals for up to three applications. Be sure to apply with a NIS surfactant. Making applications in late summer/early fall just before new growth is very effective in controlling bentgrass.
Answer last updated on: 09/06/2018