Four hundred and forty-one isolates from six populations of Sclerotinia homoeocarpa were collected from creeping bentgrass golf greens in Georgia, and tested for sensitivity to the demethylation inhibitor (DMI) fungicide, propiconazole. Mean ED50 values for an unexposed population (baseline) and an exposed population were 0.0049 and 0.0283 g ml-1propiconazole, respectively. Mean relative mycelial growth on two discriminatory concentrations was significantly (P=0.05) greater for isolates from the populations that had been exposed repeatedly to propiconazole than for isolates from the four unexposed populations. The effective period of control decreased linearly with increasing log ED50 value, ranging from a mean of 12.2 days for an isolate with an ED50 value of 0.075 g propiconazole ml-1 to 28.2 days for an isolate with an ED50 value of 0.005 g propiconazole ml-1. Based on this study, decreased in vitro sensitivity to propiconazole resulted in reduced dollar spot control.