Japanese Stilt Grass on the Coulee Experimental State Forest
An overview of control efforts from 2020 to Present
Forest Health Program: Carter Hellenbrand, Mary Bartkowiak and Erika Segerson-Mueller
Coulee Experimental State Forest
The smallest of Wisconsin’s northern state forests, the Coulee Experimental State Forest in La Crosse County, is approximately 3,000 acres and consists of upland oak forests, experimental tree plantings, open fields on ridgetops, rock outcroppings and several small “goat prairies” on steep topography.
“The CESF is owned by the state of Wisconsin but was dedicated as a USDA Forest Service Experimental Forest in 1960 for studying the effects of land use and steep land management on floods, soil erosion, and stream sedimentation” (Adams et al. 2004). Research was conducted by the Forest Service until about 1976. Although the property is still officially a Forest Service Experimental Forest, it is now mostly used for timber production and recreation.
Unfortunately, there are several species of invasive plants on the property, including buckthorn, multiflora rose, Japanese barberry and non-native honeysuckles. However, the greatest concern on the Coulee Experimental State Forest is the presence of the highly invasive Japanese stilt grass, which was first found on this property in 2020.
Japanese stilt grass (Microstegium vimineum) is an annual grass native to southeastern Asia. An aggressive spreader, Japanese stilt grass was first introduced to the United States in 1919, likely via Oriental porcelain packaging material that contained seeds (Kurtz et al. 2017). JSG is found in more than 20 states, primarily in the southeast, and the population in the Coulee Experimental State Forest is the first and only known location in Wisconsin at this time.
Japanese stilt grass can grow in sun or shade; its shade tolerance makes this species of particular concern within forested areas. Dense patches of stilt grass can quickly spread and shade out other vegetation and impede tree regeneration. One plant can produce 1,000 seeds each year which remain viable in the soil for over 5 years, although most seeds tend to germinate in the first year. Larger populations require more extreme action, often involving herbicide and/or burning. Early Detection/Rapid Response is critically important for eradication of this aggressive grass.
Data collecting during Japanese stilt grass survey
Spring
A pre-emergent herbicide, such as Oust, is applied to area of known populations prior to germination.
Japanese stilt grass infestation
Summer
As a warm season grass, JSG remains relatively small until late summer when accumulated temperatures allow for substantial growth. Pre- and post-emergent herbicides can be considered at this time.
Japanese stilt grass seeds
Late Summer to Early Fall
On the Coulee Experimental State Forest, Japanese stilt grass begins to flower mid-September and continues until the end of the growing season. Surveys begin mid-August and end when the grass has senesced. On the Coulee Experimental State Forest, we have opted to burn small population with a propane torch and spot treat/burn each stem and the surrounding area.
01 / 07
Japanese Stilt Grass Identification
Japanese stilt grass mixed with native vegetation
While grasses can be challenging to correctly identify, Japanese stilt grass has several unique characteristics. For starters, the leaves have a noticeable silvery midrib that is slightly off-center.
Japanese stilt grass silvery midrib
Japanese stilt grass usually has multiple weak stems with branching rootlets (or stilts) near the base. The root system is also weak, thin and pulls out of the ground easily while white grass has a well developed root system.
Japanese stilt grass root system
In fall, the stems and upper leaves turn purple or brown in color, giving the plant its other common name, Nepalese browntop.
A common look-a-like for Japanese stilt grass is White grass (Leersia virginica). Besides the identifying characteristics of Japanese stilt grass above, a key to identification is touching the stem.
The stems of White grass have hairs at the nodes (pictured) while the stems of Japanese stilt grass are smooth.
Another look-a-like species is spotted lady's thumb (Persicari maculosa). This non-grass species is often mistaken for Japanese stilt grass due to its similar leaf size and shape.
The key difference for this species are the pink flowers that appear in July to September. Japanese stilt grass flowers are not pink and first appear in September and persist into the fall.
2020
Japanese stilt grass surveying on the Coulee Experimental State Forest
The first control work done on Japanese stilt grass in the Coulee Experimental State Forest was in July of 2020. Foliar spot treatment was performed using Milestone, a post-emergent herbicide (red polygon).
2021
Japanese stilt grass infestation
The first pre-emergent herbicide used on Japanese stilt grass, Oust, was added in May of 2021 (red polygons). This herbicide was applied to the soil where populations were noted the previous growing season.
Letters regarding the aggressive nature of this grass were sent to nearby landowners, increasing awareness to help prevent this species from spreading further.
A transect survey was completed in July (green circles) and August of 2021 (orange triangles). Wisconsin DNR staff followed transect lines 200’ on either side of road between parking lot 1 and 2 (yellow striped polygon). The 5 crew members walked no further than 10’ apart which allowed for field of vision overlap. All populations were mapped.
Glyphosate was applied to the previously surveyed plots of Japanese stilt grass via foliar spot application following the transect surveys in July (green polygons) and August (orange polygons) of 2021.
01 / 05
2022
Japanese stilt grass mixed with other vegetation
In the spring of 2022, Oust was applied to the areas identified during the 2021 surveys (yellow polygons).
Glyphosate was applied using a foliar spot treatment in June 2022 on plots of Japanese stilt grass (red polygons).
A contractor was hired to survey and control all populations of Japanese stilt grass. In July and early August of 2022, Japanese stilt grass was surveyed for along Russlan Coulee Rd. and walking trails on the Coulee Experimental State Forest. The crew used a mixture of Oust and glyphosate (red polygons) to spot treat these populations as they were found.
During a site visit, Wisconsin DNR staff noticed new populations of Japanese stilt grass occurring near the parking area and along a trail. The contractor resurveyed the area and these new populations were burned using a propane torch (red points).
01 / 06
2023
Japanese stilt grass torched area
In August 2023, stream surveys were conducted on the Coulee Experimental State Forest by Wisconsin DNR staff. The first survey was conducted by following the shoreline of a drainage/dry creek bed (red polyline) and the second followed the shoreline of Dutch Creek (purple polyline). Surveyors started at the orange point and ended at the green point for each survey. Japanese stilt grass was not found during either of these surveys.
On September 2nd, 2023, a contractor was hired to do a survey of Japanese stilt grass locations on the Coulee Experimental State Forest using the Invasive Plant Survey. Each of these locations were recaptured using an EOS Arrow sub-meter. This device decreased the margin of error greatly, making each plot easy to find and control.
These locations are depicted as green diamonds while the blue triangles are the locations of UW-La Crosse graduate student Evan Chalmers' research plots (to learn more, check out the "Field Observations" section).
Based on these points, populations were burned via propane torch on September 20th, 2023. The Japanese stilt grass seed pods had yet to shatter and the stems were still green.
A follow up survey was completed by Wisconsin DNR staff on October 4th, 2023. All points were located and mapped using the EOS Arrow (orange diamonds). Very few seed pods had begun to shatter and the stems/leaves were just beginning to turn purple.
These additional points were burned via propane torch on October 16th, 2023. About half of the seed pods had either completely shattered or begun to shatter. The purple stems and leaves had become much more common. A final survey was completed November 14, 2023. No populations were found.
01 / 05
2024
Japanese stilt grass mixed with other vegetation
The plots that were previously found in 2023 were spot sprayed using the pre-emergent herbicide Oust (yellow polygons) on April 1st.
The first survey of 2024 was completed by Wisconsin DNR staff on August 19th and 20th. These populations of Japanese stilt grass were found along Russlan Coulee Rd, parking lots and walking trails (blue triangles). Each of these populations were burned using a butane torch.
Surveys by DNR staff were performed once again on September 16th (red triangles). Another survey was done on September 30th (yellow triangles). All of these plots were burned using a butane torch immediately after discovery and were mapped.
The next survey was completed on October 16th, 2024. Each of these new populations were mapped and burned with a butane torch (green triangles). DNR aquatic invasive species staff performed surveys along nearby drainage ditch and creeks. No populations were found.
A final survey was done along Russlan Coulee Rd on October 31st, 2024, but no new populations were found.
01 / 05
Location Comparison by Year
Leaf litter next to a trail on the Coulee Experimental State Forest
All Japanese stilt grass locations found in 2020 (white triangles) compared to all locations found in 2021 (orange squares).
All Japanese stilt grass locations found in 2021 (orange squares) compared to all locations found in 2022 (green triangles).
All Japanese stilt grass locations found in 2022 (green triangles) compared to all locations found in 2023 (yellow squares).
All Japanese stilt grass locations found in 2023 (yellow squares) compared to all locations found in 2024 (blue triangles).
Field Observations
Data logger on the coulee experimental state forest
Cage containing Japanese stilt grass
Area marked for butane torch
DNR staff using a butane torch
Color change of Japanese stilt grass
Cleistogamous Japanese stilt grass flower
Opened cleistogamous Japanese stilt grass flower
Seed shattering of Japanese stilt grass
Left to right starting on the top: UV shield with data logger underneath, JSG cage for Evan Chalmers Research, JSG marked plot before burning, burning JSG with a butane torch, JSG color changed stem and leaves, closed cleistogamous flower, opened JSG cleistogamous flower with seeds, JSG stem with evidence of shattering seeds
UW La Crosse Graduate Research
Evan Chalmers, a University of Wisconsin La Crosse graduate student, completed his research on the phenology of Japanese stilt grass on the Coulee Experimental State Forest in 2023. His research, partially funded by the Wisconsin DNR, deployed data loggers to monitor the conditions around three research plots. Early in 2022, one of the plots was vandalized and the plot was aborted. The remaining two plots collected data on ambient air, soil temperature and light levels. In the fall of 2023, a cage was placed over one the plots to detect seed shatter. Evan collected the first flowering Japanese stilt grass specimen in mid-September 2022. This research has played a crucial role in understanding when Japanese stilt grass begins to flower which guides survey, control and overall management of this invasive grass.
Additional Notes
Repeated visits in September and October of 2023 allowed Wisconsin DNR staff to observe Japanese stilt grass at different life stages including a collection of a cleistogamous flowers/seeds; likely a first here in Wisconsin. These are asexual flowers that develop within the leaf sheath, are self-fertile and therefore genetically identical to the parent plant. Because of these cleistogamous flowers and, thereafter, seeds, it is not recommended to hand pull Japanese stilt grass and leave it on site. These cleistogamous seeds shatter later than those produced by open pollination. Various other stages of seed shattering were also observed.
Based on these control efforts through 2024, utilizing a pre-emergent herbicide in the spring followed by burning new populations with a butane torch beginning in the middle of August has had the most success. Since Japanese stilt grass puts on significant growth later in the season, it makes sense to do visual surveys beginning mid-August and to repeat these surveys monthly through the end of the growing season. A grass-specific herbicide could eventually be used in the spring to decrease the amount of damage caused to surrounding vegetation, thereby increasing native competition.
Resources
Adams, M.B., L. Loughry, and L. Plaugher. 2004. Experimental Forests and Ranges of the USDA Forest Service. Gen. Tech. Rep. NE-321. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 178 p.
Anderson, C., A. Bartz, E. Epstein, and D. Feldkirchner. 2008. Rapid Ecological Assessment for the Coulee Experimental Forest, La Crosse County, WI. Natural Heritage Inventory Program. Bureau of Endangered Resources, Madison, WI: PUBL ER-809. 42 p.
Evans, Christopher. “Species Profile - Japanese Stiltgrass.” Illinois Extension, University of Illinois Urbana-Champaign, 18 May 2021, extension.illinois.edu/blogs/naturalist-news/2021-05-18-species-profile-japanese-stiltgrass.
Evans, C.W., N.J. Loewenstein, C.T. Bargeron, C.E. Barlow and D.J. Moorhead. 2012. Field Guide To The Identification Of Japanese Stiltgrass: With comparisons to other look-a-like species. Alabama Cooperative Extension System, ANR-1457. 12 p.
Kurtz, Cassandra M.; Hansen, Mark H. 2017. An assessment of Japanese stiltgrass in northern U.S. forests. Res. Note NRS-247. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 5 p.
