Red stele root rot
A soil water-mould that needs cold, waterlogged ground to establish — turning the centre of a strawberry root a telltale reddish-purple and stunting the plant, prevented by a raised bed far more easily than it is ever cured.
- Pathogen
- Water-mould (Phytophthora fragariae)
- Spreads by
- Surface water, waterlogged soil, infected planting material
- Favoured by
- Cold, waterlogged, poorly drained soil
- Main risk
- Stunted, wilted plants; no cure once established
Overview
Red stele root rot, caused by the water-mould Phytophthora fragariae, is one of the most serious root diseases of strawberry wherever the crop is grown in cool, wet conditions, India included. It is a genuinely distinct pathogen from the Phytophthora species behind other diseases on this site — late blight (P. infestans), pepper foot rot (P. capsici) and avocado root rot (P. cinnamomi) are all different species with different hosts and different weather preferences.
The disease takes hold specifically in cold, waterlogged, poorly drained soil, which is exactly why strawberry is grown on a raised bed everywhere in India rather than on flat ground. An affected plant is stunted and wilted, often with a dull blue-green or reddish tinge to the leaves and poor fruit set, symptoms that can look like simple water stress until a taproot is dug up and split open lengthwise to reveal a reddish-purple core inside an otherwise ordinary-looking root — the "stele" that gives the disease its name and the confirming sign growers look for.
How to identify it
- Stunted, wilted plants with a dull blue-green or reddish tinge to the foliage, often patchy across a bed rather than uniform.
- Poor flowering and weak fruit set on an otherwise established planting.
- A taproot split lengthwise shows a telltale reddish-purple core inside an otherwise normal-looking root — the confirming sign, since above-ground symptoms alone can look like plain water stress or nutrient deficiency.
- Worst in the lowest-lying, wettest patches of a bed or field, often appearing there first and spreading outward in a wet season.
What causes it and when
- Phytophthora fragariae is a soil-borne water-mould, not a true fungus — it produces swimming spores that move through water in the soil, which is why it spreads fastest and establishes most readily in cold, waterlogged, poorly drained ground.
- It is a genuinely distinct species from the Phytophthora pathogens behind late blight, pepper foot rot or avocado root rot — resistance or management learned for one does not transfer to another.
- It also travels in surface irrigation water and on infected runners or tissue-culture plantlets from an already-affected nursery or planting.
- Once established in the soil, the pathogen can persist for several years, which is why prevention through bed design and clean planting material matters far more than any treatment afterward.
Cultural & organic control
- Always plant on a well-drained raised bed, never on flat or low-lying ground that can hold water even briefly — this single practice is strawberry's main defence against the disease anywhere in India.
- Buy only certified, disease-free runners or tissue-culture plantlets from a reputable nursery, and never take runners from an old or declining planting.
- Avoid moving soil, tools or irrigation water between an affected bed and a healthy one.
- Where a bed has had red stele, avoid replanting strawberry there for several years, since the pathogen persists in the soil.
Chemical control
- There is no reliable in-soil cure once red stele is established in a plant or a bed — chemical options are preventive, not curative.
- A recommended systemic fungicide drench at planting can help protect a new bed in a tract with a known history of the disease; confirm the current product and dose with your local KVK or state horticulture department, since options and approvals change.
- Chemical treatment is never a substitute for a well-drained raised bed — it is, at best, an additional layer of protection on top of correct bed design.
Prevent it coming back
- Fix the drainage, not just the symptom — a properly formed, well-drained raised bed prevents red stele far more reliably than any spray applied after symptoms appear.
- Never replant strawberry directly into a bed where the disease has already appeared; the pathogen persists in the soil for years.
- Source planting material only from certified, disease-free nurseries every season, since strawberry is replanted fresh each year in India anyway.
- Scout low-lying, poorly drained patches of a field first and most often, since that is where the disease establishes and spreads from.
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 strawberry plants look stunted and a bit wilted in the lowest part of the bed. What is wrong?
This is a classic pattern for red stele root rot, caused by the soil water-mould Phytophthora fragariae, which needs cold, waterlogged, poorly drained ground to establish — exactly the conditions a low-lying patch provides. Dig up an affected taproot and split it lengthwise: a reddish-purple core inside an otherwise normal-looking root confirms the disease. There is no cure once it is established — focus on improving drainage immediately and avoid replanting strawberry in that spot for several years.
Is red stele the same disease as the Phytophthora blight or root rot I've read about on other crops?
No — Phytophthora fragariae (red stele, on strawberry) is a genuinely distinct species from Phytophthora infestans (late blight, on potato and tomato), Phytophthora capsici (pepper foot rot) and Phytophthora cinnamomi (avocado root rot). They share a genus and a general preference for wet conditions, but each is a separate pathogen with its own host range, so management learned for one does not automatically transfer to another.
Why does every strawberry guide insist on a raised bed?
Because red stele needs exactly the cold, waterlogged, poorly drained conditions that flat or low-lying ground provides, and strawberry cannot tolerate waterlogging at all. A well-formed, well-drained raised bed — together with drip irrigation rather than furrow flooding — is the single most effective and lowest-cost defence against this disease, far more reliable than any fungicide applied after the fact.
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.