Sclerotinia minor Jagger myceliogenic sclerotial germination, growth, infection, and colonization of peanut (Arachis hypogaea L.) tissue was optimum at 20-25 C. Ninety-five to 100% relative humidity (RH) for more than 12 hours was necessary for germination. There was no difference in infection and colonization of main stem versus lateral branch tissue but younger plants were more susceptible than older plants. Correlation and regression analyses were conducted on data from field experiments with artificially and naturally infected plants. Important independent variables in regression models for lesion length (LL), weekly change in lesion length, or disease severity index (DSI) were: number of days with temperature ≤16.7 C (DA17), the interaction of DA17 with precipitation (DA17*P), RH, maximum temperature (TMAX), and plant height for the week prior to disease measurement, and TMAX, P, and soil moisture (SM) at 0 to 5-cm for the period two weeks prior to disease measurement. were studied in field Infection and disease development plots with modified canopy.Ph. D.