eXtension

nemblewell weed

Asked April 26, 2017, 3:06 PM EDT

My lawn service detected nimblewell weed last year. This year is has spread a lot. My lawn service first recommend tenacity and now is reluctant to use.
How can I find someone who has experience with tenacity?

Hennepin County Minnesota

1 Response

Are you certain the lawn weed is nimblewill? The plant is uncommon in Minnesota, at least according to the following map:
https://www.invasive.org/browse/subinfo.cfm?sub=6068

Is it possible the plant is actually bentgrass? Use this resource to carefully check the identification of your lawn weed:
http://purdueturftips.blogspot.com/2014/04/weed-of-month-for-september-2013-is.html

In any case, Tenacity has been approved for use to control nimblewill and bentgrass. Is lack of experience with Tenacity the only reason your lawn service is reluctant to use it? If you are unsure, ask the company representative to clarify this.

We don't know what Twin Cities area lawn care companies, if any, might recommend and apply this product in your circumstances.

Experts at Purdue University have this to say about products used to control nimblewill:

"Mesotrione (Tenacity) can be used for selective control of nimblewill growing in a cool-season turf. To control nimblewill, start applying mesotrione in the spring (late-April) with a nonionic surfactant at 0.25% (v/v). You will need to make two or three applications. If you make three applications, use the 5 fl oz/A rate (or 6, 6 and 4 fl oz/A). The product does have a yearly maximum use rate, and the label states “do not apply more than 16 oz of Tenacity per acre per year or per crop (equivalent to a maximum of 0.50 lb of mesotrione per acre per year).” You can also apply mesotrione in late summer and fall, but you should initiate them by August for best results.

Another option is to apply topramezone (Pylex) at 1-1.5 fl oz/A at 21- to 28-day intervals starting in late April. For best results, include a methylated seed oil at 0.5-1.0% (v/v)."

Purdue experts also note that perennial grasses can be "controlled by spot-treating with a nonselective systemic herbicide such as glyphosate (Roundup). For best results, apply when the plants are young and actively growing. However, because nimblewill is capable of re-establishing through surviving stolons, at least two glyphosate applications are recommended, but three or more may be needed for complete eradication. It is important to allow the weed to regrow before making any follow-up applications."

After the grassy weeds are killed, the affected areas must be cleared and repaired with seed or sod.