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Ber (Ziziphus mauritiana Lam.) is an ancient and poor man's fruit crop grown in semi arid and arid regions of India and other few countries. The powdery mildew of ber incited by Oidium erysiphoides f. sp. ziziphi Yan & Wang (Microsphaera alphitoides f. sp. ziziphi Griffon & Maublanc) is a major disease in India, causing great loss in productivity and quality of fruits. To know the effect of different abiotic environmental factors on the development of the disease, a field experiment was conducted during 1993 to 2000 on susceptible ber cultivar 'Jogia'. On the basis of seven years data on epidemiology of ber powdery mildew, it was observed that the disease initiation took place during 39-46 standard meteorological weeks. During this period the average maximum and minimum temperatures of 32.0 and 13.8 degrees C; average morning and evening relative humidities of 75.8 and 41.4%, respectively and average rainfall of 4.04 mm were recorded. The peak percent disease index (PDI) was observed in December. During this period the average maximum and minimum temperatures of 24.7 and 4.9 degrees C; average morning and evening relative humidities of 82.6 and 35.7%, respectively were observed. Temperature had significant and humidity had non-significant correlation with PDI. Matrix studies indicated that there was a significant relation between PDI and temperature. It was also found that the correlation coefficient of determination (R-2) was 0.1269 for abiotic factors explained the variation in the ber powdery mildew incidence to the extent of 12.69%.