Regulation of black rot (Diplodia seriata) in organic apple production (BIOFRUITNET Practice Abstract)

Summary

Removal of fruit mummies also has a preventive or infestation-reducing effect against the storage rot pathogens Neofabraea alba and N. perennans.
Practical recommendation
•Due to their tendency to form fruit mummies (Picture 4), some apple varieties are especially at risk of black rot infestation. These include Gerlinde, Elstar, Dalinbel, Natyra, Ingrid Marie and Wellant
• Infections are favoured by high temperatures (20-26°C) and prolonged rain events
• Heavy rainfall causes spores to be washed out of the fruit mummies, which then cause infection on the young fruit via the lenticels
Prevention:
• Choose robust varieties
• Look for infection hint on fruits and leaves:
o First infections may become visible from the beginning of June
o Leaf spots ("frog eyes") may appear on the leaves near infested shoots or fruit mummies (Picture 1), and black necrotic infestations form on the fruit (Picture 2), which later grow to the size of a pinhead and develop a red edge
o From August onwards, the outbreak of brown rot can occur from these primary infections as shown in (Picture 3).
• Pick out fruit mummies consistently each year by hand before sprouting (February/March)