Superficial scald (scald) is one of the major physiological disorders that occur during cold storage of apples and pears.
Scald is characterised by brown irregular patches that appear on the skin during long-term cold storage.
These areas become sunken and turn deeper brown as the disorder develops.
Although the damage is only superficial, this amount of damage greatly downgrades fruit quality and grower returns.
Postharvest storage disorder
Scald is a postharvest storage disorder of some important apple varieties, particularly Red Delicious and Granny Smith, and is essentially a long-term storage disorder.
It can be seen within three months of harvest and increases with time in storage.
Scald symptoms develop only slowly in cold storage but they rapidly increase in severity within a few days at normal air temperatures.
Treatment
1-methylcyclopropene (1-MCP) is a registered treatment in Australia for inhibiting superficial scald while maintaining apple quality during storage.
It is registered in Australia for use inapples to:
reduce incidence of superficial scald and peel greasiness
maintain firmness
maintain titratable acidity
reduce incidence of mealiness.
DPA
Scald can be effectively controlled with diphenylamine (DPA) as a postharvest dip or drench.
This treatment should be applied as soon as possible after harvest—delaying treatment by 14 days or more, greatly reduces the effectiveness of DPA.
Download the Orchard plant protection guide
See this article in Tree Fruit Jan 2020
