| Japanese stiltgrass [Microstegium vimineum (Trin.) A. Camus] is a nonnative, invasive grass of management concern throughout the eastern United States. Conventional management recommendations emphasize removal of Japanese stiltgrass in autumn prior to flowering. Investigations of the reproductive biology of Japanese stiltgrass were conducted to assess considerations that impact such management strategies. Japanese stiltgrass flowered in response to short-days, but no flowering occurred under long-days. Inflorescences from natural stands of Japanese stiltgrass were harvested at four reproductive growth stages: one raceme branch beginning to emerge through the leaf sheath, one raceme branch fully elongated with a second branch visible, fully expanded inflorescence, and in concert with natural seed dispersal. Germination of seeds from these harvests averaged 13%, 51%, 95%, and 100%, respectively, suggesting management designed to prevent seed production should be implemented before inflorescences are visible. Japanese stiltgrass seeds displayed primary innate dormancy upon natural dispersal, with <1% of seeds stored 0 or 15 days germinating. Yet, >95% of seeds stored 90 days germinated. Light was not required for germination. The efficacy of three selective postemergence herbicides (fenoxaprop-P, imazapic, and sethoxydim) applied May, June, or August were compared. Averaged across application timings, the herbicides controlled Japanese stiltgrass 86% and reduced seedhead production 87%. Compared to no herbicide treatment, seedling emergence the subsequent spring was reduced 89%, 70%,and 78% by fenoxaprop-P, imazapic, and sethoxydim, respectively. Additionally, fenoxaprop-P or sethoxydim applied twice at half or full-labeled rates controlled Japanese stiltgrass, providing 92% biomass reduction and 98% seedhead reduction. A 3-year experiment was conducted at forested sites to document the ecological impacts of management of Japanese stiltgrass on native flora recruitment and establishment. Management treatments included hand-removal, mowing, or glyphosate applied in autumn compared to season-long control by hand-removal or fenoxaprop-P. All management treatments reduced populations of Japanese stiltgrass over time compared to no management. Relative cover and seed bank populations of Japanese stiltgrass decreased over time with consecutive years of management. However, selective management was more suitable than nonselective management for recruitment and re-establishment of native plants and increasing overall species richness. |
