How to reduce the incidence of potato soft rots

Soft rots are a range of warm weather bacterial diseases, usually Erwinia spp, that enter the tubers through mechanical damage and rots the tubers in storage.

How to reduce incidence of potato soft rot diseases

Correct balanced nutrition of the crop prior to harvest, particularly calcium and boron nutrition can have positive effects against soft rots.

Crop Nutrition and Potato Soft Rots


Evidence show that strengthening the tuber cell wall with calcium can help reduce the severity of Erwinia soft rot in storage.

Calcium effect on potato soft rots

This study shows the relationship between calcium availability, peel calcium content and weight loss caused by Erwinia soft rot.

High levels of calcium in the tuber also reduce bruising risks at harvest and subsequent transportation. Varieties vary in their calcium uptake, however, using calcium nitrate rather than ammonium nitrate maximizes uptake, reduces the risk of damage allowing ingress of disease.

Calcium uptake by potato variety

This trial from the USA shows that the use of calcium nitrate rather than ammonium nitrate resulted in higher levels of calcium in tubers over a range of different varieties.


Alongside potassium, calcium and magnesium, boron is an important element present in the cell wall. Here it acts as cement between pectins, providing cohesive strength for cell tissues. Therefore boron affects tuber storage quality characteristics. Boron also affects calcium absorption, so supplies are important to ensure a balanced nutrition.

Effect of boron on calcium levels in potato tubers

This trial shows how boron influences the calcium content of tubers and so also the incidence of internal rust spot.

Other crop management practices reducing potato soft rots

  • Harvesting early, thereby minimising late disease ingress or tuber deterioration
  • Taking care during harvest and grading to reduce physical damage and bruising
  • Disinfecting seed storage areas to reduce disease carry over 
  • Harvesting in good conditions to avoid physical damage and disease infestation. 
  • Using in-store treatments (e.g. fungicides) to reduce tuber disease build-up 
  • Controlling tem peratures and humidity in storage