Bacterial soft rot
A soft, watery, foul-smelling bacterial rot of fleshy vegetables that enters through wounds and spreads fast in warm, wet conditions and storage.
- Pathogen
- Bacteria (Pectobacterium/Dickeya)
- Spreads by
- Soil & water; wounds; contact in store
- Favoured by
- Warm, wet, poorly-ventilated conditions
- Main risk
- Fleshy tissue rots to foul mush; store losses
Overview
Bacterial soft rot is caused by soft-rot bacteria (Pectobacterium and Dickeya, formerly Erwinia) that break down the fleshy, water-rich tissue of many crops — potato tubers, onion bulbs, cabbage and cauliflower heads, tomato fruit and other vegetables. The affected tissue turns into a soft, watery, cream-to-brown mush, usually with a characteristic foul, offensive smell, while the outer skin may stay intact until it collapses.
The bacteria are common in soil and water and enter only through wounds — growth cracks, insect or mechanical injuries, harvest and handling bruises. They multiply explosively in warm, wet, poorly-ventilated conditions, in waterlogged soil, and in warm, moist storage, so soft rot is both a field and a post-harvest/storage disease. Because there is no effective bactericide once the rot spreads, management is about avoiding wounds, keeping the crop and store dry and well-ventilated, good drainage, and careful curing and grading before storage.
How to identify it
- Fleshy tissue (tuber, bulb, head or fruit) turning into a soft, watery, cream-to-brown mush.
- A characteristic foul, offensive smell from the rotting tissue.
- Outer skin often intact at first, then collapsing as the inside liquefies.
- Fast spread in warm, wet field patches and in warm, moist storage, rotting neighbouring produce by contact.
What causes it and when
- Soft-rot bacteria (Pectobacterium/Dickeya) that are common in soil and water and enter only through wounds.
- Wounds from growth cracks, insects, mechanical/harvest injury and handling bruises open the door.
- Multiply fast in warm, wet, poorly-ventilated conditions, waterlogged soil and warm, moist storage.
- Both a field disease and a major post-harvest/storage rot of potato, onion and cole crops.
Cultural & organic control
- Avoid wounds — handle gently at harvest and grading, and control insects that injure the produce.
- Ensure good drainage in the field and avoid waterlogging; harvest in dry conditions, not wet.
- Cure and dry produce properly before storage, and grade out any cut, bruised or diseased pieces.
- Store cool, dry and well-ventilated, and rotate crops away from repeatedly-affected land.
Chemical control
- There is no effective spray to cure a bacterial soft rot once it spreads — control is preventive.
- Where recommended, a copper-based or other registered bactericide can reduce field spread as part of hygiene.
- Focus effort on wound-avoidance, drainage, curing and clean, ventilated storage rather than chemicals.
- Confirm any recommended product and store treatment for your crop with your local KVK.
Prevent it coming back
- Make gentle handling, dry harvest, proper curing and careful grading the routine before storage.
- Keep fields well-drained and stores cool, dry and ventilated, and remove rotting pieces promptly.
- Control injuring insects and rotate away from land that repeatedly develops soft rot.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
My potatoes/onions have turned into a soft, smelly mush. What is it?
That soft, watery, foul-smelling breakdown of the fleshy tissue, often under an intact skin, is bacterial soft rot (Pectobacterium/Dickeya). The bacteria enter through wounds and multiply fast in warm, wet conditions and moist storage. There is no cure once it spreads, so remove rotting pieces at once, dry and ventilate the store, and next time handle gently, harvest dry, cure properly and grade out damaged produce.
Why does soft rot get so much worse in storage?
Because warm, moist, poorly-ventilated storage is ideal for the bacteria, and stored produce is packed in contact so the rot passes from one piece to the next. Any wound or bruise from harvest and handling gives the bacteria an entry, and a single rotting tuber or bulb can spread through the heap. Curing and drying before storage, grading out damaged pieces, and keeping the store cool, dry and ventilated are what hold it down.
How do I prevent bacterial soft rot?
Since the bacteria only enter through wounds and thrive in wet warmth, prevention is about wounds and moisture: handle the crop gently at harvest and grading, control insects that injure it, keep fields well-drained, and harvest in dry conditions. Then cure and dry the produce, grade out any cut or bruised pieces, and store cool, dry and well-ventilated. There is no rescue spray, so this hygiene is the whole control.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.