Phoma macrostoma is a fungus being developed as a natural herbicide (bioherbicide) for selective weed control in turfgrass. Previous research with this product is limited to cool-season turfgrass, and information is limited on appropriate application rates or efficacy at higher temperatures and weeds associated with warmseason turf. Field studies were conducted in College Station, TX to evaluate efficacy of the bioherbicidefor slender aster (Aster subulatusvar. ligulatus Shinners) control in common bermudagrass. In 2011, applications of 128 g m-2, split-applied between days 0 and 28 resulted in good control (88%); however, 64 and 32 g m-2 rates failed to provide adequate control. In 2012, single applications of 128 gave excellent control (94%), while the 32 and 64 g m-2 rates gave poor control (54 and 68%, respectively) relative to untreated plots.No injury to common bermudagrass occurred in either study.