Effect of Weather Parameters on Development of Powdery Mildew of Ber (Ziziphus mauritiana) Caused by Oidium erysiphoides

India’s one of the most popular fruits is the ber (Ziziphus mauritiana Lamk.). Ziziphus mauritiana is sometimes referred to as Indian plum or desert apple. Oidium erysiphoides f. sp. Ziziphi, which causes powdery mildew of ber, is more common and a threat in northern states. The white powdery coating on leaves and fruits affects the photosynthesis and growth & development, respectively. This disease results in 50-60% loss in fruit yield and reduces market value of the produce. In the present study, the effect of abiotic environmental elements such as temperature, relative humidity, wind speed, and others were observed and they had a significant impact on the progression of powdery mildew disease. In the study, which was carried out on two ber cultivars viz., Gola and Kaithali, the disease progression on both cultivars showed a significantly negative correlation with maximum (Tmax) and minimum temperature (Tmin) and a significantly positive correlation with morning (RHm) and evening relative humidity (RHe). The favourable weather variables were observed viz., Tmax above 20.3 °C, Tmin around 9.9 °C and RHm was more than 80%. The ber cultivar Gola was more susceptible to disease development than Kaithali, with Gola having the highest disease intensity.