Cultural control (Apple scab)

  • Prune trees to allow good air circulation and rapid drying of leaves to reduce scab risk.
  • Remove wood scab during winter pruning.
  • After harvest and before leaf fall, apply a spray of 5% urea to the trees.  Urea encourages microflora that speed up leaf breakdown and increase the palatability of leaves to earthworms, which are mainly responsible for leaf litter disposal in orchards.
  • Urea also directly affects the scab fungus by preventing formation of the sexual state.
  • Earthworms remove leaf litter better from bare soil than from grass.  Therefore, keep the grass well mown to encourage earthworm activity.
  • Mow leaves in autumn to macerate for more rapid leaf decomposition.  Maceration of leaves can decrease scab inoculum by up to 90%.
  • Even where leaves are trapped in hedges maceration can reduce inoculum by 50-60%.
  • Brushing machines can be used to sweep leaf litter from under trees into alley ways for maceration.
  • Where leaf litter still remains in the spring or weather conditions have made action in the autumn impossible, mow to macerate leaves in spring.
  • A spray of 5% urea to leaf litter in spring will also encourage leaf rotting and prevent ascospore release.