Greenhouse trials, using experimental inoculation, were carried out with the aim to evaluate the efficacy of sodium bicarbonate at two rates (500 and 1000 g/hl), compared with two fungicides (Dinocap and Bupirimate) to control powdery mildew on tobacco. The colonization of the untreated tobacco leaves was complete 30 days after the inoculation, later on spots became necrotic and basal leaves died. Inoculation methods using 105 conidia/ml suspended in 0.1% sterile water agar showed constant and reproducible results. Sodium bicarbonate was more effective at 1000 g/hl, and no phytotoxic symptoms were observed on tobacco leaves after the applications. An increased disease severity was observed after repeated applications of sodium bicarbonate at 500 g/hl, while its efficacy was higher at 1000 g/hl and a most satisfactory control was reached after three applications. A similar trend to sodium bicarbonate at 1000 g/hl was observed for Dinocap application. Sodium bicarbonate applications did not affect the technological properties of cured tobacco leaves.