News: Japanese Stiltgrass

News: Japanese Stiltgrass

 

(Microstegium vimineum) is a shade tolerant, annual C4 grass. It is a straggling plant, usually 36” in height, and
the reclining stems can grow up to 40” long. Its stems are typically branched, rooting at the lower nodes, and
the nodes and internodes are smooth and hairless. The long narrow leaf blades are 2-4” long sparsely hairy
on both surfaces, and distinctly tapered at both ends. The ligules are membranous and are 0.5-2.0 mm
long. M. vimineum is native to India and Japan. It possesses characteristics typical of many invasive
species: it grows quickly, fruits within a single season, produces abundant seed, and easily invades habitats
that have been disturbed by natural (e.g., flood scouring) and anthropogenic (e.g., mowing, tilling) sources.
It is locally abundant, able to displace native wetland and forest understory vegetation with its dense,
expanding monospecific patches. It is usually found under moderate to dense shade in moist conditions, but it
does not persist in areas with periodic standing water, nor in full sunlight. Manual or mechanical techniques may be the best
method for controlling M. vimineum, since it is a shallowly-rooted annual. Hand pulling, however, is extremely labor-intensive,
is feasible only for small infestations, and will need to be repeated and continued at least seven years to exhaust the seed
supply in the seed bank. Mowing may be an effective control method if carried out in late summer, when the plants are in peak
bloom but before seed is produced. For extensive infestations, where mechanical methods are not practical, systemic
herbicides such as imazameth (Plateau) or glyphosate (RoundUp, or Rodeo in wetland sites), or grass-specific herbicides like
fenoxaprop (Acclaim), sethoxydim (Vantage or Poast). the next spring typical pre-emergence herbicides for crabgrass will
provide season-long control.

Randy Prostak of Amherst University of Massachusetts