In organic apple growing protective applications with copper, sulphur or lime sulphur are
used for apple scab control. Protective applications have to be repeated when new leaves
unfold. The timing of protective sprays depends on the weather forecast. If forecasted
infection conditions fail to appear, treatments were for nothing. With curative control
agents available, the number of treatments could be reduced. In greenhouse trials we
tested control agents for their protective and curative efficiency against apple scab after
artificial inoculation of potted apple trees. Applications were done 2 hours before
inoculation, 5 hours after inoculation on wet leaves, 5 hours after inoculation during
simulated rainfall or 24 hours after inoculation on wet or dry leaves. The optimal time of
application differed between the preparations tested. Vitisan and OmniProtect had their
highest activity when sprayed curative 24 hours after inoculation. Combinations were
found, which revealed a high efficiency against apple scab from 2h before to 24 hours after
inoculation. In a field trial apple scab was effectively controlled by curative applications of
OmniProtect
