Herbicide-based Weed Management in Miscanthus sacchariflorus

Although miscanthus is well known for its fast growth and high biomass productivity, its plant establishment and early growth are sensitive to weed interference. Thus, greenhouse and field experiments were conducted to establish an herbicide-based weed management system with pre-emergence (PRE) and post-emergence (POST) herbicides and their sequential applications. The plant establishment and early growth of miscanthus in the first 2 years of planting were significantly affected by weed interference, resulting in a greater than 90 % biomass yield loss in an untreated weedy control in which no herbicide was applied. PRE applications of S-metolachlor, alachlor, and pendimethalin were safe for M. sacchariflorus under both greenhouse and field conditions and showed good weed control under field conditions. POST applications of all of the tested auxinic herbicides, bentazon, thifensulfuron, and mesotrione were safe for M. sacchariflorus and showed good weed control. Sequential applications of PRE (S-metolachlor, pendimethalin or isoxaflutole) and POST herbicides (dicamba, bentazon, or mesotrione) showed better weed control than did their sole applications, resulting in better establishment. In particular, the sequential application of either S-metolachlor or pendimethalin followed by mesotrione showed the most effective weed control (85 % less weeds than the untreated weedy control) with good safety for M. sacchariflorus and thus provided the best early establishment and biomass yield. The mesotrione-based sequential application achieved approximately 15.4 ton ha⁻¹, 79 % of weed-free control in the second year of establishment. Therefore, our results suggest that the sequential applications of PRE and POST herbicides are essential for the first and second year of M. sacchariflorus cultivation.