Soft rot diseases of potatoes

Page last updated: Friday, 11 August 2017 - 12:46pm

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Management

Although there is no cure for potato soft rot — due to the ability of the bacteria to multiply and spread rapidly — correct management techniques can minimise the risk of infection. These are shown in Table 1.

Table 1 Management techniques for soft rot infection (Pectobacterium species) in potatoes
Growth stage Symptoms Management
Pre-plant Soft rot present in the seed
  • Grade out infected tubers.
  • If cutting seed, sterilise the knife after every bin/box/bag to prevent spread to healthy tubers.
  • Clean shed equipment frequently, especially grading/sorting rollers. Several chlorine-based disinfectants are available for sterilising equipment.
  • Apply fungicides if required to prevent other diseases.
  • Maintain adequate crop rotations.
Planting

  • Do not plant in a wet paddock or if soil temperatures are above 20°C.
  • Avoid planting tubers that have moisture on them.
Growing crop

Non-emergence, wilting and/or yellowing of plant tissue, blackened cracks appearing on stems, water-soaked lesions on base of stems

  • Do not overwater.
  • Minimise nitrogen application to prevent large bushy crops that have high leaf wetness.
  • Control weeds as these can harbour soft rot bacteria.
  • Monitor and record areas where potato stems have black cracks appearing. These are areas with high bacteria counts and should be harvested separately to minimise potential soft rot spread in storage.
Harvest/grading Large amount of mechanical damage
  • Ensure tubers are mature at time of harvest.
  • Slow the harvester/grader speed to minimise damage.
  • Disinfect bins prior to tubers being placed in them.
  • Avoid harvesting in wet conditions.
  • Do not leave tubers in direct sunlight or at temperatures above 20°C.
  • Dry tubers as soon as possible after harvest to remove excess soil.
  • Minimise dust in storage areas as this spreads the bacteria.
Coolstore Rot in bins
  • Cure the seed appropriately before placing in coolstore.
  • Maintain adequate airflow throughout coolstore to prevent carbon dioxide buildup.
  • Cool seed gradually to prevent condensation build-up on the surface.
  • Apply fungicides to prevent other diseases. Some inorganic and organic salt-based products containing copper, sodium and potassium have shown effectiveness against soft rot bacteria but none of these products is registered in WA and should not be applied solely for soft rot control or eradication.
  • Maintain and clean shed and storage area regularly.
  • If soft rot occurs, separate infected seed from healthy seed.

 

Contact information

Andrew Taylor
+61 (0)8 9780 6241

Soft rot diseases of potatoes

Author

Andrew Taylor