Nimblewill is a grassy weed. Technically it’s a warm season grass, but it’s commonly a problem in cool season lawns. It creates a dense mat of grass that goes dormant quickly as fall approaches leaving thick brown patches throughout the lawn.
The only known way to kill Nimblewill is with Tenacity / Mesotrione or to use Glyphosate (which will kill good grass as well). When using Tenacity you’ll want to repeat applications, every 7-10 days until it’s dead. But it’s important to remember that as it’s a warm season grass you’ll only be able to kill it during warm temperatures. If it has already gone dormant in the fall, or hasn’t come out of dormancy in the spring, you won’t be able to kill it.
One of the easiest ways to notice nimblewill is with the morning dew. It will give off a different look so you’ll notice the patches easier. It blends in during the hotter summer months so I find this trick helpful for monitoring progress.
Because it spreads easily it’s best to not do any dethatching or aerating until it has been controlled. I’ve found that it spreads very easily, even after thinking I killed it off completely I’ve found more. So do everything you can to prevent spreading until it’s taken care of.
Related ingredients: Mesotrione