Technical Abstract: During field testing of a bioherbicidal strain of the fungus Myrothecium verrucaria (MV) for control of spurges and purslanes in tomato plots in 2005, we noted extensive damage to volunteer morning-glory (Ipomoea spp.) seedlings. This observation prompted investigations on the biological control efficacy of this fungus on various Ipomoea species. Seven morning-glory species were grown in the greenhouse and tested in the first to second leaf growth stage. MV spores (107spores mL-1) were applied in Silwet L-77 surfactant or an invert emulsion. After application, the plants were placed in a dew chamber (15-18 h) and then transferred to a greenhouse. Injury caused by MV was assessed using a visual rating scale, and by fresh and dry weight determinations at termination of the tests. Ivyleaf (Ipomoea hederacea), moonvine (Ipomoea turbinate), and palmleaf (Ipomoea wrightii) morning-glories were relatively tolerant to MV, while pitted (Ipomoea lacunosa), multi-color (Ipomoea tricolor), moonflower (Ipomoea alba), and cypressvine (Ipomoea quamoclit) morning-glories were highly sensitive. Although some of these plants exhibited tolerance to spray applications of MV plus Silwet L-77, formulations of MV combined with the invert emulsion generally increased susceptibility. Results indicate differential bioherbicidal activity of MV among closely related species, i.e., Ipomoea (morning-glories), and that the invert emulsion can increase the efficacy of MV in some instances.