How do I control nimblewill in my lawn?
Nimblewill (Muhlenbergia schreberi) is a warm-season perennial grass. Nimblewill is a thin, wiry grass that is pale green or gray-green. It spreads by aboveground shoots or stolons, often forming circular spots in the lawn. Nimblewill is easy to spot in the lawn because it greens up late in spring and turns brown in early fall.
Nimblewill is difficult to control in bluegrass lawns as control options are limited. One way to control nimblewill infested areas is to completely destroy the nimblewill with an application of glyphosate (Roundup). Another option is to dig up and destroy the nimblewill. Bluegrass or other cool-season grasses have to be reestablished by seeding or sodding after the nimblewill is completely destroyed.
An application of a selective herbicide is another control option. Tenacity (mesotrione) is a systemic herbicide that selectively controls nimblewill in bluegrass lawns. (It is also safe for perennial ryegrass, tall fescue, and the fine-leaf fescues.) Tenacity is currently not available to home gardeners. It must be applied by lawn care professionals. When treated with Tenacity, nimblewill stops growing, turns white, and eventually dies. Three applications (at two to three week intervals) are usually necessary to control nimblewill. Occasionally, white tips can also be seen on Kentucky bluegrass and other cool-season grasses following treatment. This is a temporary symptom, as the white grass tips will be removed during subsequent mowings.