Abstract Powdery mildew (Sphaerotheca mors-uvae) severely infects young shoots, stems and fruits of gooseberry (Ribes uva-crispa). Environmental friendly and biological control measures are being sought throughout the world. Especially in organic gooseberry growing effective control measures are needed, because powdery mildew infections may result in a total loss of the crop. In a field trial the effect of potassium bicarbonate (Armicarb) on powdery mildew of gooseberry was evaluated. Four treatments; i.e. two preventive strategies and two curative strategies, were applied. Plants were sprayed until runoff. The percent of infected berries, shoots and disease severity were assessed. Very high disease incidences were observed in the untreated control. All potassium bicarbonate treatments significantly reduced the powdery mildew severity in leaves and fruits compared to the untreated controls. The preventive strategies were very successful. However, the number of spray applications was high.