Suppression of cogongrass (Imperata cylindrica) by a bioherbicidal fungus and plant competition

Abstract

The possibility of using the fungusBipolaris saccharias a bioherbicide to suppress cogongrass and to allow the establishment of bahiagrass in cogongrass–bahiagrass mixed plantings was investigated under greenhouse conditions. The bioherbicide was prepared by mixingB. saccharispore suspension containing 105spores ml−1with an oil emulsion composed of 16% horticultural oil plus 10% light mineral oil and 74% sterile water. The bioherbicide caused severe foliar blight in cogongrass and slight phytotoxic damage on bahiagrass. In the first experiment, the bioherbicide reduced cogongrass biomass without affecting bahiagrass biomass. In the second experiment, the bioherbicide caused a 64% reduction in fresh weight, a 74% reduction in the number of rhizomes, and a 47% reduction in the height of cogongrass. The latter experiment also showed an increase in bahiagrass fresh weight in the presence of cogongrass when the bioherbicide was applied. This study indicates the potential of combining bioherbicide application with competition from a desirable grass species as a strategy for the integrated management of cogongrass.