Andropogon vimineus Trin., Eulalia viminea (Trin.) Kuntze (Fernald 1950), Microstegium vimineum var. imberbe (Nees ex Steud.) Honda,  Microstegium imberbe (Nees ex Steud.) Tzvelev,  Microstegium willdenowianum Nees ex Steud., Pollinia viminea (Trin.) Merr., Nepalese browntop

M. vimineum also resembles native Leersia virginica (Whitegrass) and both plants often grow together. Several characteristics can distinguish M. vimineum from Leersia virginica. M. vimineum has hairless stem nodes, all thin roots, and densely compacted flowers while Leersia virginica has hairy stem nodes, some thick rhizome roots, and sparse open flowers (Mehrhoff 2000).

M. vimineum can both self- and cross-pollinate by producing either cleistogamous (CL, self-pollinating flowers) or chasmogamous (CH, cross-pollinating flowers) spikelets, flowers, and seed.  It overwinters in a seed bank, which can be viable for between 1 to 4 years depending on the environmental conditions (Barden 1987; Gibson et al. 2002; Judge et al. 2008; Redwood et al. 2018). A single late-season drought can reduce seed bank viability enough to prevent overwintering (Gibson et al. 2002; Webster et al. 2008). Seed germination can take up to 90 days (Judge 2005), and seed banks are reported to withstand temperatures down to -23°C (Redman 1995). The type and quantity of spikelets and seeds produced are dependent on the level of water stress on the plant and light intensity. Inundation promoted CL spikelet production and favorable water levels instead promoted CH spikelets (Gibson et al. 2002; Campbell et al. 2016). Fecundity of M. vimineum declined in habitat with less than 10% of full sun (Claridge and Franklin 2002; Huebner 2011). M. vimineum grown in sunny habitat produced significantly more CL spikelets than those in shaded (2-8% full sun) habitat and the number of CH spikelets did not differ between the habitats (Cheplick 2006). Reports of seed production volume by M. vimineum vary considerably with some publications citing individual plants producing 5 to 50 seeds (Cheplick 2005; Cheplick 2010) and others between 100 to 7000 seeds (Gibson et. al 2002; Wilson et al. 2015). Dense populations of M. vimineum can produce nearly 1000 seeds per m2 (Emery et al. 2013). Further, Warren et al. (2012) stated that as few as 1 to 3 plants can produce enough seeds for a population to persist. CL spikelets produce up to 50 seeds per plant, nearly double the seeds of their CH counterparts (Cheplick 2005). However, CL seeds are smaller and viable for less time than CH seeds, making CH seeds more likely to be the primary source in seed banks (Huebner 2011). Further, seeds produced under drier conditions have significantly less mass than those from mesic environments (Huebner 2011). Spikelet and seed production in both CL and CH inflorescences were decreased in shaded habitat (Cheplick and Fox 2011) but increased with soil moisture and leaf litter thickness (Warren et al. 2013). Self-pollinating CL flowers and seeds are a low-energy alternative to their CH counterparts that can provide a competitive advantage against invasive M. vimineum colonizers where resources (e.g. light and water) and pollinators are limited (Price and Jain 1981; Cheplick 2008). Another advantage of M. vimineum is its ability to spread via clonal lateral tillers (Cheplick 2006).

Seed dispersal is facilitated by flowing water in low-lying wet pathways, animals, and human activity. Local distance in dispersal of M. vimineum seeds via water averages 0.21 to 1 meter per year and is strongly correlated with precipitation (Huebner 2010; Miller and Matlack 2010; Rauschert et al. 2010; Schramm and Ehrenfeld 2012; Teikala and Barney 2013). In southwest Virginia, the farthest recorded M. vimineum seed dispersal via stormwater was 2.4 meters in one month (late January to February) that also received 52.32 mm of rain (Teikiela and Barney 2013). During high water events, M. vimineum seeds float and can disperse throughout an entire wetland or alluvial floodplain (Woods 1989; Mehrhoff 2000).

Seeds can adhere to animal fur or clothing and may be dispersed through endozoochory (seed dispersal through ingestion) in large herbivores (Merhoff 2000; Williams and Ward 2008). Road and trail maintenance can also spread M. vimineum seeds when soil and gravel are relocated, with local dispersal reported up to 273 meters by road grading (Christen and Matlack 2009; Mortensen et al. 2009; Mikhailova et al. 2017; Rauschert et al. 2010, 2017).

Several native herbivorous insects consume Microstegium vimineum. Seven different species of insects acquire >35% of their carbon from M. vimineum, with nearly 100% derivation by Neoconocephalus sp. (katydid nymph), Largus sp. (bordered plant bug), and Dendrocoris sp. (stink bug nymph). However, M. vimineum survival and growth were not affected by insect herbivory (Bradford et al. 2010).

Grazers such as white-tail deer typically avoid consuming M. vimineum (Averill et al. 2016), however, M. vimineum seeds have been germinated from deer droppings, indicating potential endozoochory (Williams and Ward 2008).  Herbivore grazing of more favorable, co-occurring plants reduces competition and can increase the abundance of M. vimineum (Eschtruth and Battles 2009; Knight et al. 2009; Bourg et al. 2017; Averill et al. 2018; Faison et al. 2019).

Spread of M. vimineum in the United States occurs rapidly in disturbed land, both natural (e.g flood scouring, fire) and artificial (e.g. mowing, tilling). Population expansion typically requires dispersal agents (e.g. running water, hikers, landscaping) (Manee 2008; Christen and Matlack 2009; Mortensen et al. 2009) with most spread occurring from rivers, ditches, and roads into surrounding wildlands (Hunt and Zaremba 1992). Spread within the Great Lakes basin is mainly attributed to human-mediated transport as a consequence of forest road management and construction (Christen and Matlack 2009; Mortensen et al. 2009; Rauschert et al. 2010, 2017). Also, M. vimineum spread is exacerbated by the removal of the plant litter layer (Oswalt and Oswalt 2007; Vidra et al. 2007; Marshall and Buckley 2008).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic	Beneficial

Realized:

Microstegium vimineum can quickly outcompete or replace existing vegetation, and fill vacant niches. Its fast growth and adaptations to low light allowed it to reduce tree and other native plant regeneration through shading of the sub-canopy (Leict 2005; Oswalt et al. 2007; Flory 2010). Notably, suppression of native plants by M. vimineum can promote secondary invasion of other non-indigenous plants (e.g. garlic mustard Alliaria petiolata) (Flory and Bauer 2014). M. vimineum’s high biomass production leads to large amounts of leaf litter, which is a physical barrier to tree seedling establishment (Flory and Clay 2010). Abundant leaf litter also supports earthworm populations which can alter decomposition mechanisms and shift nitrogen saturation to be dominated by NO3-  which favored the spread of M. vimineum and other invasive species (Gilliam 2006; Nuzzo et al. 2009; Davalos et al. 2015).

Alterations to local soil chemistry by M. vimineum invasion have been shown to favor its growth and spread over native species. M. vimineum’s high nitrogen demand promotes the activity of nitrifying cycling bacteria and archaea, leading to increased nitrification rates and transformation of ammonia to nitrate (Lee et al. 2012; Rodrigues et al. 2015;  Shannon-Firestone et al. 2015; Rippel et al. 2020). A larger nitrate pool benefited M. vimineum growth and spread, resulting in increased soil pH that further increased nitrification rates (Kourtev et al. 1998, 2002; Ehrenfeld et al. 2001). Carbon-cycling is also impacted by M. vimineum invasion. Its rapid growth and effect on soil microbes accelerated carbon-cycling, resulting in a net loss of soil carbon which may have implications on long term soil fertility (Strickland et al. 2010; Strickland et al. 2011; Craig and Fraterrigo 2017; Craig et al. 2019). In contrast, Shannon et al. (2012) found that invaded plant communities that had high native species diversity were not significantly negatively impacted by M. vimineum alterations to nitrogen cycling. Also, rapid increases in soil pH and phosphorus availability following M. vimineum invasion may reduce microarthropod community diversity and favor mite abundance in leaf litter (McGrath and Binkley 2009).

Allelopathic effects exhibited by M. vimineum decreased germination of Raphanus sativus (common radish) by ~60%, but impacts on native plants have been insignificant to date (Pisula and Meiners 2010; Corbett and Morrison 2012; Cipollini and Greenawalt Bohrer 2016). It is a reservoir for pathogens such as Bipolaris sp. (leaf blight disease) and has prompted pathogen emergence and amplification which resulted in spillover to native species (Flory et al. 2011; Kleczeweski et al. 2012; Stricker et al. 2016).

Invasion of the forest floor by M. vimineum and the subsequent reduction in herbaceous plant cover reduced arthropod abundance and richness across multiple trophic levels (Marshall and Buckley 2009; Simao et al. 2010). These altered trophic interactions between native insect species reduced the abundance of Anaxyrus [Bufo] americanus (American toad) in invaded forests (DeVore and Maerz 2014). M. vimineum facilitated declines in sub-canopy habitat in New Jersey deciduous forests may have resulted in the decline in abundance of some guilds of birds between 1980 to 2005 (Baiser et al. 2008).

Microstegium vimineum has a high socio-economic impact in the Great Lakes.

Historical ecosystems may be lost through a loss of species diversity (Leict 2005; Flory 2010). Continuous removal and prevention (labor, chemicals, time) may be costly (Flory 2017). M. vimineum can infest lawns and gardens and become a visual and physical nuisance. Its control is advocated for by various extension offices and landscape companies ( Hubbard 2018; GreenTurf 2019; NYIS 2019). It’s fast growth and adaptations to low light allowed it to reduce tree and other native plants regeneration through shading of the sub-canopy which could negatively impact the timber industry (Leict 2005; Flory 2010).

There is little or no evidence to support that Microstegium vimineum has significant beneficial impacts in the Great Lakes.

Potential:

Due to its fast growth and high biomass in shaded habitat, M. vimineum invasions have been shown in some instances to promote insect abundance and diversity despite a reduction in native plant species (Metcalf and Emery 2015).

In Wisconsin, Microstegium vimineum is listed as a prohibited species under Wis. Admin. Code § NR 40, making it illegal to possess or transport within the state. In Ohio, it is classified as a restricted invasive plant under Ohio Admin. Code § 901:5-30-01 prohibiting its sale, propagation, distribution, import, or intentional dissemination.  In New York,  M. vimineum is prohibited and cannot be knowingly possessed, sold, imported, purchased, introduced, or propagated under 6 NYCRR Part 575. Indiana added M. vimineum to its Prohibited Invasive Terrestrial Plant list (312 IAC 18-3-25) on 4/18/2020, banning its sale, gift, barter, exchange, distribution, transport, and introduction. As of 2017, Pennsylvania lists M. vimineum as a “Rank 1” invasive plant, but legislation only covers species defined as “Noxious Weeds”.  Explicit regulations are not defined for Microstegium vimineum in Michigan, Minnesota, Illinois, or Ontario.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control

Biological
Pathogenic fungi in the Bipolaris species, including Bipolaris zeicola (Kleczeweski and Flory 2010) and Bipolaris Mv. (Kleczeweski et al. 2012), can cause leaf blight disease in many plants, including Microstegium vimineum. Infection results in lesions on the foliage and stem of M. vimineum and reduced seed head production, wilting, and occasional plant death (Kleczeweski and Flory 2010). Due to the destructive effects Bipolaris fungi can have, it has been suggested as a potential bioherbicide for invasive species such as M. vimineum. However, its application is highly impractical because Bipolaris can infect and harm a wide range of grasses and plants that co-occur with M. vimineum (Flory et al. 2011; Kleczeweski et al. 2012).

Physical
Mowing and hand-pulling can be effective methods of controlling small infestations and retaining native species. Both methods are best employed in summer and early fall (June-September) when plants are tall, but prior to seed set (Judge et al. 2008; Flory and Lewis 2009; Ward and Mervosh 2012; Shelton 2012). M. vimineum can regenerate from its seed bank for approximately 5 years after removal, thus physical control must be implemented every year until the seed bank is depleted (Tu 2000; Czarapata 2005; Flory 2010). Flooding continuously for 3 months can also kill the plants, however, it may not destroy soil-stored seed (Tu 2000).

Prescribed fire can be used to clear M. vimineum leaf litter and biomass, however, caution should be taken because future recruitment and M. vimineum biomass were greater in burned vs. unburned sites as it thrives in disturbed landscapes (Glasgow and Matlack 2007; Emery et al. 2013; Wagner and Fraterigio 2015). Alternatively, directly burning the plant stalks with propane torches is an effective treatment method but must be repeated annually (Ward and Mervosh 2012).

Forest management regimes can also be used to discourage M. vimineum colonization. In northeastern US deciduous forests, M. vimineum invasion was reduced by keeping canopy openings below 15%, excluding deer, and seeding the understory with native species (Heubner et al. 2018).

Chemical
A wide range of herbicides can be used to control Microstegium vimineum at a variety of timings and doses (listed as kilograms of active ingredient per hectare), in particular, pre- and post-emergence. The application of grass specific post emergent herbicides (e.g. clethodim, sethoxydim, pendimethalin, fenoxaprop-P , fluazifop-P, imazapic, pendimethalin, and fenoxaprop-p-ethyl) are the most effective herbicide at controlling M. vimineum and are best applied annually or bi-annually using a backpack sprayer to limit the unintended application to non-target plants. Broad spectrum foliar herbicides (e.g. glufosinate and glyphosphate) are nonspecific and kill native and non-target woody plants and can reduce species richness. If used, these chemicals should be applied shortly after germination (Flessner et al. 2019).

Herbicide application post-emergence can result in various control effects on M. vimineum, including reduced plant density and size, reduced seed head and seed production, and preventing emergence the year following treatment. M. vimineum density and size in a deciduous forest was reduced by at least 87% eight weeks after treatment using clethodim (0.1 kg a.i./ha), fenoxaprop-P (0.1 kg a.i./ha ), fluazifop-P (0.3 kg a.i./ha), sethoxydim (0.5 kg a.i./ha), or glufosinate (1.1 kg a.i./ha), but annual applications are needed to maintain control (Judge et al. 2005a;b). Following herbicide application in late July for two consecutive years, M. vimineum cover and seed head production was reduced to below 5% (untreated control 90%) at the end of the growing season and emergence was prevented a year after the second application using imazapic (0.140 kg a.i./ha), pendimethalin (3.36 kg a.i./ha) plus pelargonic acid (11.8 kg a.i./ha), fenoxaprop-p-ethyl (0.045-0.180 kg a.i./ha), glufosinate (0.14 -0.56 kg a.i./ha), 5% vinegar, or glyphosate (0.14-0.56 kg a.i./ha) (Ward and Mervosh 2012). Judge et al. 2005b, 2008 also found post-emergence glyphosate (2.2 kg a.i./ha) to be 100% effective at controlling M. vimineum. Fluazifop-P, when used at 0.21 kg a.i./ha post-emergence, effectively controlled and removed. Yearly re-application of any herbicide is recommended for maximum control of M. vimineum.

Cool-season forage grass approved aminopyralid (0.05 kg a.i./ha) or aminopyralid (0.05 kg a.i./ha) plus metsulfuron (0.001 kg a.i./ha) visually reduced M. vimineum by 70-90% 12 weeks after treatment (Flessner et al. 2019). The grass specific herbicide, sethoxydim, applied in July reduced M. vimineum cover from 80% to 20% by the end of the growing season but reapplication every year is required for continued control (Frey and Schmidt 2015).

See also:

Midwest Invasive Plant Network Invasive Plant Control Database