Abstract: Scab (Venturia inaequalis on apple and V. pirina on pear) is the key parasite on pipfruits. Seventy five % of the pesticide use in apple production is related with control of fungaldiseases, in which apple scab has a share of 70%. This high pesticide use is subjected to a greatpressure due to the competition between retailers and supermarkets to reduce the maximumresidue level on the fruits. Furthermore, consumers are more sceptical about the presence ofpesticide residues on fruits. Reduction in pesticide use is possible, for example, by takingalternative control measures against scab. Pear scab, and to a lesser extent apple scab, does notonly infect fruits and leaves, but gives rise to twig lesions as well. The presence of twig scabrepresents a major problem, especially in organic pear growing, as fruit growers lack satisfyingmeasurements to put an end to the disease. Furthermore, as the use of copper is under discussion,new alternative control strategies are a must in the organic farming. To this end, the efficacy ofpotassium bicarbonate (pbc) to control apple scab was investigated. The mode of action of pbc onconidial infection and the timing of applications in function of the infection period wasdetermined. Out of the first trials it was concluded that pbc has a fungistatic activity and has thebest activity towards apple scab when it is applied curatively.