Herbicide phytotoxicity response and eradication studies in Miscanthus x giganteus
Past and current research with a novel bioenergy crop, Miscanthus x giganteus (Mxg)—a perennial C4 grass native to East Asia being studied as a potential bioenergy feedstock in the U.S.—were reviewed. Aspects of Mxg research surveyed include its taxonomy, biology, breeding and genetics, end uses and environmental benefits, agronomy, production economics, need for weed control, invasiveness potential and methods of control. Weed control was found to be critical during the first one to two years of establishment. The assumption has been made that herbicides used in cereal crops can be safely used in Mxg, and several such herbicides have been used successfully in European plantings. The invasive potential is believed to be very low, and no research has been conducted thus far to evaluate methods of control. Greenhouse and field experiments were conducted in 2007 to 2009 to evaluate the phytotoxic response of Mxg to several preemergence and postemergence herbicides applied at various rates. No herbicides with activity on only broadleaf weeds reduced above-ground biomass or produced visible injury in Mxg. Several herbicides reduced biomass yield or produced injury, and some, particularly those with significant activity on grass weeds, reduced dry mass and produced visible injury. Results support the hypothesis that herbicides used in corn are safe to use on Mxg and provide new potential herbicide options for use in establishing Mxg. A greenhouse experiment in 2008 investigating the dose-response of Mxg to glyphosate showed that Mxg greenhouse-grown plantlets were controlled with as little as 360 g ae/ha glyphosate. Three field experiments were conducted in 2007 to 2009 to evaluate various methods of controlling a mature stand of Mxg. The first experiment involving fall- and spring-applied glyphosate showed that fall, spring, and fall followed by spring applications significantly reduced above-ground biomass the summer following spring treatments and that summer shoot number was significantly reduced following sequential fall and spring applications. The second experiment demonstrated that both tillage and a single glyphosate application significantly reduced above-ground dry biomass, and that tillage in combination with one or two glyphosate applications provided the highest level of control in the same growing season. These experiments indicate that tillage and glyphosate can control a mature Mxg stand, but treatments will likely need to be employed for at least two growing seasons for complete eradication. The third experiment examined the feasibility of planting glyphosate-resistant soybean directly into a mature stand of Mxg following conventional tillage. Results showed that soybean yield was not reduced when one or two sequential glyphosate applications were made in-crop compared with a weed-free control. The same field was subsequently rotated to glyphosate-resistant corn following deep tillage in 2009 with the same treatment scheme implemented. Corn yield results were similar to those from the soybean experiment. The Mxg population was also reduced from the previous season, but complete eradication was not achieved. This experiment showed that rotation from a mature field of Mxg directly to a glyphosate-resistant soybean-corn rotation under conventional tillage practices appears to be possible with no significant yield loss although Mxg eradication will likely take more than two seasons.
Miscanthus, Miscanthus x giganteus, herbicides, phytotoxicity, eradication, control
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign