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Potatoes: post-harvest disorders and handling

Author: Natalie Hoidal

From hollow heart to soft rot to freeze damage, we've seen a whole host of potato issues this fall. This article provides an overview of these issues and management tips for each.

Hollow heart

Image: Ben Phillips,
Hollow heart, the formation of an irregularly shaped hole in the center of potatoes, is caused by alternating periods of rapid and slow growth. We see this occur when we have excessive moisture followed by dry periods, and when soil fertility is not managed well. Often after really wet weather we welcome drier periods, but it's important to monitor soil moisture and irrigate when necessary to prevent symptoms like hollow heart.

Hollow heart does not affect the flavor or safety of potatoes, but customers who purchase potatoes with this condition may think that something is wrong and throw them out, or choose to purchase from someone else in the future.

Tips for managing hollow heart:
  • If you have some hollow heart in this year's potatoes, let your customers know that their potatoes are still safe to eat, and that this is simply a symptom of wet and erratic weather conditions. 
  • Monitor soil moisture: consider making higher hills to help with drainage, use a soil moisture meter to inform irrigation choices, consider using straw mulch
  • Fertility: over fertilization sometimes results in hollow heart. Make sure to get regular soil tests and make fertility decisions based on soil test results. Use the Nutrient Management Guide for Commercial Fruit and Vegetable Growers to calculate fertilizer needs for each crop you grow.
  • Large potatoes are more likely to get hollow heart. Consider a smaller variety, or plant large varieties closer together. 

Soft rot

Photos: Gerald Holmes,
Soft rot is a bacterial disease caused by Pectobacterium species. These bacteria live in the soil, and can also survive in decaying plant debris and seed potatoes. The bacteria enter potatoes through wounds, bruises, or injuries, which often occur during harvest. If some of the harvested potatoes contain one of these pathogens, it can quickly spread to other potatoes in storage through wounds and bruises.

Tips for managing soft rot:
  • Rotate your crops:  do not plant nightshades in the same location for as long as possible (ideally 4 years), and manage weeds well. Some wild nightshades can host soft rot pathogens.
  • Sanitize all harvest equipment and your storage facility regularly.
  • Wait to harvest until tubers are mature
  • Harvest carefully to avoid bruising and other harvest damage, and sort potatoes upon harvest. Remove all damaged potatoes if you know that this pathogen is present. 
  • Maintain good ventilation in storage, dry tubers as quickly as possible, and do not wash tubers before storing them. Washing prior to storage can introduce excess moisture, and can also cause more bruising and abrasions. 
  • Cure all tubers for 2-3 weeks at 50-55 degrees F with good air flow
  • Monitor your storage areas and check regularly for wet spots and disease. 

Freeze damage

We've heard a few reports of customers calling farmers to say that their potatoes are rotten, but the potatoes at the farm still look fine and seem to be disease free. In some of these cases, we think that people are storing their potatoes in the back of the fridge where they are getting cold damage. Potatoes should not be stored below 40 degrees F; make sure to let your customers know! 

For more info on potato storage and curing vegetables, check out our page on postharvest handling.

Image: Marita Cantwell, UC Davis

 Do you have other potato questions? Let us know!

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