Abstract: In vitro studies were conducted to assess the effect of different temperatures, relative humidity and incubation period on conidial germination of Erysiphe necator (powdery mildew) at the Department of Plant Pathology, College of Agriculture, Vijayapur during 2020-22. Physiological studies of E. necator revealed that incubation of powdery mildew fungal spore suspension at various intervals indicated fairly satisfactory conidial germination from 18 to 22 hrs and ultimately reached maximum at 24 hrs after incubation in distilled water. Among the different relative humidity (RH) levels used for conidial germination, maximum germination was observed at 80 per cent RH (82.67%). howver, relative humidity ranging from 80 to 85 per cent was found suitable for conidial germination of E. necator. Maximum conidial germination (83.69%) of E. necator was observed at 25 °C after 24 hrs and optimum temperature range for the conidial germination was 20-25 °C.