Fruit Rots

Fruit rots continue to pose a problem for those of us in the wetter parts of the state. Frequent rains and warm temperatures really set the stage for bitter rot, black rot, white rot, and even brown rot. Any rain event that produced more than 2” of rain would remove the majority of fungicide, meaning that harvested fruit is going into the storage bin unprotected from these pathogens. If possible, a fungicide like Merivon or Pristine, with a zero day preharvest interval will provide protection in storage. However, fruit that may have looked clean at harvest could be infected, and any infected fruit will develop lesions over time. At this stage, damage control is limited to scouting bins, and removing infected fruit as it develops. Remember that postharvest applications of fungicide will not “cure” fruit that is already infected!

Some key points to minimizing storage rots include:

  • Using clean bins (Cleanliness is next to impossible, but we keep trying!)
  • Minimizing bruising and injury to fruit as it is picked
  • Harvesting fruit at proper maturity, as overmature fruit is more susceptible to rot
  • Keeping fruit cool after harvest. The growth of these fungi that cause rots is reduced when temps are below 44 degrees F
  • 1-methylcyclopropene (1-MCP) (e.g., SmartFresh), blocks the ethylene receptors in apples, delaying them from ripening, and thus rot.

There was an interesting study about the Canadian experience using SmartFresh, you can find here.

One rotten apple really can spoil the barrel. Which is why an ounce of prevention (or parts per million of SmartFresh or both!) is really important to a successful harvest.

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