Mechanical control methods for Japanese stiltgrass (Microstegium vimineum)

Background/Question/Methods

Japanese stiltgrass (Microstegium vimineum) is an invasive grass that poses a major threat to the biodiversity of many natural areas throughout its introduced range. While there are recommended control methods, few studies have scientifically quantified the efficacy of these control methods. A previous study determined that mowing any time after midsummer reduces the M. vimineum population, so we expanded upon this study to determine the effect of mowing height on M. vimineum populations.

We established small plots at two sites that were dominated by M. vimineum. Vegetation surveys were conducted for each plot and then plots were mowed at one of three different heights (10 cm, 5 cm, 0 cm) in late summer before seed set. After 5 weeks, prior to senescence, all vegetation in the plots was harvested. Seed spikelets were counted, dried, and weighed. Vegetation was sorted into M. vimineum vegetation and all other vegetation, then dried and weighed. 

Results/Conclusions

Mowing at any of the three heights significantly reduced seed production and seed biomass of M. vimineum. Mowing at 10 cm reduced seed production by 85.9% and mowing at ground level reduced seed production by 99.5%. Seed biomass was reduced by 92.1% when plots were mowed 10 cm and by 99.5% when mowed at ground level. The results demonstrate that mowing below 10 cm before seeding occurs can significantly reduce M. vimineum reproductive output and could be integrated into an effective management program.

However, even relatively few seeds per unit area could be enough to lead to a dominant population. A future study aims to examine the combined effects of mowing height, mowing time, and application of leaf mulch to prevent germination and seedling emergence. The results of this study could provide insight into feasible, effective management plans for homeowners, as well as local and state organizations.