Apple scab is the most economically important disease of apples worldwide.
- All parts of the tree are affected and crop losses can be severe (70% or more) when weather conditions are favourable in the early part of the season.
- Losses can result directly from fruit infection or indirectly by the effect of repeated defoliation of the tree over several seasons on subsequent growth and yield.
- Several factors influence the scab attack including varietal susceptibility, local topography, overwintering inoculum and weather conditions.