By Celestine Duncan
Japanese stiltgrass (Microstegium vimineum) is an introduced annual grass that has invaded forest lands throughout much of the eastern half of United States (Figure 1). The plant is native to Asia and was historically used for packing goods shipped from China. Discarded packaging material may have been the source of seed introduction to the United States.
Japanese stiltgrass was first reported in Tennessee around 1918 and is currently established from New Hampshire south to Florida, west to Texas and north to Iowa (Figure 2). The plant is often associated with other non-native invasive plants such as Japanese honeysuckle (Lonicera japonica), sericea lespedeza (Lespedeza cuneata) and Japanese barberry (Berberis thunbergii).
Various grass-specific and non-selective herbicides (e.g., glyphosate) have been applied to control Japanese stiltgrass. However, it is difficult to use these herbicides for stiltgrass control without causing significant injury to desirable grasses and other associated vegetation. Field trials conducted by researchers and managers show that Milestone® herbicide applied for broadleaf weed control also impacts Japanese stiltgrass. These findings are similar to observations on other invasive annual grasses such as medusahead rye (Taeniatherum caput-medusae) and downy brome (Bromus tectorum L.). For information on these two annual grasses, visit http://techlinenews.com/articles/2014/medusahead-control-with-milestone-herbicide.
RESULTS OF FIELD TRIALS
Field trials were conducted near Sweetwater, Tennessee to compare effectiveness of several broadleaf herbicides on Japanese stiltgrass. Treatments included Milestone at 5 and 7 fluid ounces per acre (fl oz/A), metsulfuron-methyl (Cimmaron herbicide) at 0.25 ounces of product/A plus 2,4-D Ester, and 2,4-D Ester alone at 1.5 pints/A. All treatments included a non-ionic surfactant at 0.25 percent. Applications were made in April when Japanese stiltgrass was four inches in height or less. There were four replications of each treatment. Visual observations of percent control were recorded about four months following application.
Results showed that Milestone at either 5 or 7 fl oz/A provided excellent control of Japanese stiltgrass for at least four months after treatment. There was no control observed with either metfulfuron plus 2,4-D Ester or 2,4-D Ester applied alone (Figure 3). Milestone controlled emerged Japanese stiltgrass and provided residual control of germinating seed during the remainder of the growing season (Figure 4).
Milestone is a selective herbicide that effectively controls invasive shrubs and broadleaf plants such as Japanese honeysuckle, sericea lespedeza and Japanese barberry that commonly grow in association with Japanese stiltgrass. Japanese stiltgrass dominance can be reduced on infested sites by applying Milestone at 5 to 7 fl oz/A at growth stages when broadleaf weeds, shrubs and Japanese stiltgrass are susceptible to Milestone. This allows land managers to control or suppress Japanese stiltgrass and other invasive plants while leaving desirable grasses intact.
Japanese stiltgrass often grows in forested areas. Information on the relative tolerance of various tree species to Milestone® herbicide is available at http://bit.ly/2pBVqwl.
More about Japanese Stiltgrass
Japanese stiltgrass is an aggressive annual grass that can impact native species diversity, reduce wildlife habitat, and disrupt ecosystem functions. Japanese stiltgrass invasion and persistence in a plant community depends on establishment from seed that remains viable in soil for five or more years. The plant also spreads by stolons during the growing season. Wind, water, animals, and humans disperse Japanese stiltgrass seed to new locations.
The invasive plant is very shade tolerant and grows primarily in moist shaded sites along riparian areas, forest edges and disturbed forest types. Roads and waterways appear to be the primary corridors for population spread.
Japanese stiltgrass is a shallow-rooted, sprawling grass that can grow to heights of about six feet, although plants are usually shorter. Plants have multiple weak stems, and tall plants may lay prostrate on the soil surface or propped against other vegetation. Aerial rootlets occur near the base of the stems. Leaves are about three inches long, lance-shaped and have a stripe of silver hairs down the mid vein of the upper leaf surface (Figure A). Flowers and fruits are borne on thin spikes on the top of a delicate stem. In the fall, the tops of plants turn purple or brown in color, giving this plant one of its common names, Nepalese browntop. In winter, the dry plants have a distinctive bright tan to orange color (Figure B).
Dow AgroSciences. 2017. Internal field trial data.
EDDMapS. 2019. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Available online at http://www.eddmaps.org/; last accessed May 31, 2019.
Fryer JL. 2011. Microstegium vimineum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
Gage KL, Gibson DJ, Evans C, Shimp J. 2010. White Paper: 2010 Stiltgrass Summit. Southern Illinois University, Carbondale. Available online at http://bugwoodcloud.org/mura/rtrcwma/assets/File/stiltgrass/Whitepaper.pdf.
Kline B and T Rogers. 2009. Milestone VM (Milestone®) and Milestone VM Plus (Capstone®) Herbicides for Forest and Natural Areas Management. Proceedings Soc. Am. Foresters. Orlando FL.
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Active ingredients for products mentioned in this article. Product (active ingredient): Milestone herbicide (aminopyralid); Cimmaron herbicide (metsulfuron-methyl).