Japanese Stiltgrass Control-Tips and Tricks

Photo of treatment area showing some reduction in Japanese Stiltgrass

Photo of control area--no treatment

What is the recommended approach for eradicating Japanese Stiltgrass?






(Note: the use of trade names in this blog or other websites does not constitute an official endorsement of these products; trade names are included for informational purposes only)



Japanese stiltgrass is a C4 grass that grows especially well in low light conditions. It is an annual, spread by abundant seed which is produced in August-September. There are a variety of control methods, including mechanical, and chemical. I personally have tried several methods to control Japanese stiltgrass, dating back to 2002 when I first encountered stiltgrass on Big Spring Bog Natural Area Preserve in Grayson County, VA.

My objective was to kill Japanese stiltgrass, but not the native herbs and grasses, thereby eventually depleting-but most likely not eliminating the seedbank. The method that appeared to work best for these objectives was a very dilute concentration of sethoxydim herbicide-often sold under the trade name of Poast (TM). The Poast label recommends mixing a 1% solution for spot treatment--I mixed the solution at .25% solution, i.e. one quart of herbicide per 100 gallons of water. This dilute concentration was sprayed in early August, timed to just precede the flowering stage of the Japanese stiltgrass.

Even at such dilute concentrations, Japanese stiltgrass was injured to the point where most (if not all) of the individuals turned brown and were unable to flower. Although there is still an abundance of Japanese stiltgrass seed in the seedbank, the photos below show that some control of the stiltgrass has occurred, allowing native vegetation a chance to rebound.

Note: applications have been made every year since 2004--and while the population has been controlled to a great extent, it is unclear whether the Japanese stiltgrass will ever be fully "controlled." The following photos show the control area, and an area where 4-5 applications of sethoxydim have been applied over the previous years. These photos were taken on the same day, and if you look closely at the treatment photo, you will still see some tell-tale lime green leaves--the emergent Japanese stiltgrass leaves.

Take home point-Japanese stiltgrass is easy to kill by the individual, but it is hard to eliminate the seedbank completely.

I've included a number of very helpful links below:
http://www.nps.gov/plants/alien/fact/mivi1.htm
http://wiki.bugwood.org/Microstegium_vimineum
http://www.invasive.org/weedcd/pdfs/tncweeds/micrvim.pdf
http://www.invasivespeciesinfo.gov/plants/stiltgrass.shtml
http://www.na.fs.fed.us/fhp/invasive_plants/weeds/japanese_stiltweed.pdf
http://www.bae.ncsu.edu/programs/extension/wqg/northcreek_images/microstegium.pdf