Slender aster (Astersubulatusvar. ligulatusShinners)is a troublesome summer annual weed that thrives under high temperatures in many areas of the southern U.S. This plant's ability to grow in a prostrate growth pattern allows it to survive mowing, making it problematic in southern turfgrass. Slender aster can be difficult to control if not treated early on in its growth cycle, because it becomes woody as the season progresses, necessitating repeated herbicide applications. Early summer applications of synthetic herbicide formulations, 2,4-D+MCPP+Dicamba, do provide good control of slender aster (Paul Baumann,personal communication), but the focus of this study was to evaluate the activity of the bioherbicide on slender aster.