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What is Clubroot?
Clubroot or Plasmodiophora brassicae is a serious soil-borne disease that affects brassica crops such as oilseed rape, cabbage, cauliflower, broccoli and brussels sprouts.
Clubroot is widely distributed and thrives in warm, moist, acidic soils, particularly in long-standing brassica growing areas.
The disease causes characteristic swollen galls on the roots, which restrict water and nutrient uptake. This weakens the plant, reduces vigour, and ultimately results in stunted growth, wilting, and significant yield losses.
Clubroot is especially damaging in oilseed rape crops, where early infection can result in widespread crop failure.
An integrated disease management approach is crucial for managing clubroot pressure and protecting future crop productivity.
What causes clubroot in brassicas?
Clubroot is caused by P. brassicae, a microscopic soil-borne pathogen that infects the roots of brassicas. The pathogen persists in the soil for up to 20 years in the form of long-lived resting spores.
Sclerotinia infected leaf
Sclerotia infected stem
How do you identify clubroot in crops?
Signs of clubroot can mainly be seen on the root system, which becomes massively swollen and distorted, with a loss of the finer roots. The early symptoms of clubroot are often difficult to detect above ground. However, as the disease progresses, the following signs may be observed:
- Wilting and yellowing of leaves, especially on warm days
- Stunted or uneven crop growth
- Poor plant establishment in affected areas
Below ground, characteristic symptoms include:
- Swollen galls on roots, misshapen, or club-like roots
- Root rot in severe cases, often accompanied by secondary infections
- Poor root development and fewer fine roots
Symptoms often appear in patches, particularly in lower-lying or poorly drained areas of the field. Root inspection is essential for confirming clubroot presence.
Sclerotinia infected leaf
Sclerotinia infection on stems
This cycle is heavily influenced by soil pH, temperature, moisture, and cropping practices. The most damaging infections typically occur early in the growing season when conditions are most favourable for spore germination and root colonisation.
Why is clubroot a problem?
Clubroot is a significant problem for UK growers due to its persistence, rapid development under suitable conditions, and potential to cause severe yield loss, especially in young plants.
Resting spores can survive for up to 20 years in the soil, making eradication extremely difficult, and infected crops experience poor root development, leading to water stress, reduced nutrient uptake, and stunted growth.
Yield losses of 10% are common in infected oilseed rape fields but can exceed 50% in severe outbreaks, and clubroot infection in vegetables like cauliflower or cabbage can result in total crop failure. There are currently no options for controlling clubroot with fungicides or biocontrols.
Sclerotinia infected leaf
Sclerotinia infection on stems
Sclerotinia infected leaf
Sclerotinia infection on stems
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Content sources
- https://ahdb.org.uk/knowledge-library/targeted-management-of-clubroot-in-oilseed-rape
- https://www.rhs.org.uk/disease/club-root
- https://ahdb.org.uk/knowledge-library/targeted-management-of-clubroot-in-oilseed-rape
- https://ahdb.org.uk/knowledge-library/an-introduction-to-clubroot-and-its-management-in-oilseed-rape
- https://ahdb.org.uk/knowledge-library/how-to-identify-clubroot-symptoms-and-map-infested-land
- https://www.bspp.org.uk/combatting-clubroot-disease-a-plant-pathology-highlight/