Emergence and seed production of woolly cupgrass (Eriochloa villosa) in legume forage crops

Woolly cupgrass is an annual grass of East Asian origin now present in North America, particularly in the US corn belt. The species was found in Canada in 2000 (southern Quebec). New, mostly small, populations have been discovered every year since 2007 and the species became a nationally regulated and quarantined weed in 2011. In order to evaluate the potential use of perennial legumes to reduce established populations, the emergence pattern, density, biomass and seed production of a woolly cupgrass population were evaluated in plots either kept unmanaged (control), in chemical fallow (treated with sequential applications of glyphosate) or cropped with alfalfa or clover from 2009 to 2011. Every year, woolly cupgrass seedlings started to emerge early (Apr. 29 to May 05) and continued to emerge over a 26- to 85-d period. All unmanaged weekly cohorts produced seed. Woolly cupgrass in unmanaged control plots produced about 10 000 seeds m(-2) in 2010 and 2011. In the chemical fallow, emergence counts decreased by about 2/3 each year. No woolly cupgrass seeds were collected during forage harvests except during a single late cut. However, despite the control of the initial spring cohort (using herbicide) and a standard cutting regime, seedbank inputs from woolly cupgrass increased every year in the forage plots. Therefore, the inclusion of perennial legumes into a rotation is unlikely to reduce the local abundance of woolly cupgrass.