Miscanthus is a perennial rhizomatous C4 grass being evaluated in the United States as a potential bioenergy feedstock. Weed control during the first two growing seasons is essential for successful establishment. No herbicides are currently labeled for use in Miscanthus grown for biomass, but herbicides used on field corn might be safe to Miscanthus. Greenhouse experiments were conducted in 2007 and 2008 to evaluate the response of Miscanthus to numerous preemergence (PRE) and postemergence (POST) herbicides. Herbicides with activity only on broadleaf species, whether PRE or POST, did not exhibit injury or reduce Miscanthus biomass. Several herbicides, particularly those with significant activity on grass species, exhibited injury ranging from 6 to 71% (scale of 0 to 100) and/or reduced Miscanthus dry mass by 33 to 78%, especially at the highest rates applied. Field experiments were conducted in 2008 and 2009 with a selection of the herbicides used in the greenhouse experiments to evaluate the response of Miscanthus to herbicides applied PRE, POST and PRE followed by POST. Results from the field experiments generally confirmed those from the greenhouse experiments. PRE herbicides and herbicides with broadleaf-specific activity generally did not produce significant injury or reduce aboveground biomass while herbicides with grass activity tended to cause injury ranging from 22 to 25% and/or reduce biomass by 69 to 78%. With some exceptions, results support prior suppositions that herbicides used in corn are safe to use on Miscanthus and may provide potential herbicide options that growers can use when establishing Miscanthus.

Nomenclature: Miscanthus, Miscanthus × giganteus Greef and Deuter ex Hodkinson and Renvoize; corn, Zea mays L.