Plant Problem Diagnostic
Clubroot (Plasmodiophora brassicae): Identification and Cultural Management
The short answer
Clubroot is a soilborne disease caused by Plasmodiophora brassicae that infects the roots of cabbage-family (brassica) crops, including cabbage, broccoli, cauliflower, Brussels sprouts, kale, kohlrabi, radish, turnip, and mustard. The classic symptom is swollen, distorted, club-shaped or galled roots. Above ground, affected plants often look stunted, yellowed, and wilt on hot days because the deformed roots cannot take up water and nutrients well.
The pathogen produces resting spores that survive in soil for many years, and it is favored by wet, acidic soils. There is no cure for an infected plant, so management is cultural and long-term: avoid moving infested soil, remove and dispose of affected roots, improve drainage, raise soil pH toward neutral where recommended, use resistant varieties if available, and rotate out of brassicas for several years. Confirm the diagnosis and get pH guidance from your local Extension before amending.
How to identify it
- Swollen, distorted, club-shaped or galled roots (dig a plant to check)
- Stunted, yellowed tops that wilt in midday heat and may recover at night early on
- Poor growth and reduced yield across cabbage-family plants
- Symptoms concentrated in wetter, more acidic parts of a bed
Conditions that favor it
- Wet, poorly drained soils
- Acidic soil (pH below neutral)
- Warm soil temperatures in the range extension sources cite as favorable (roughly 64 to 77 F)
- Resting spores already present from previous infected crops or cruciferous weeds
Cultural management steps
- 1Prevent soil spread — Avoid moving infested soil on tools, boots, and equipment, and do not compost or dump infected roots where the soil can spread.
- 2Improve drainage and raise pH — Improve drainage and, where a soil test and Extension advise it, lime the soil toward a neutral pH, which suppresses the disease; follow the recommendation.
- 3Use resistant varieties and clean transplants — Plant clubroot-resistant brassica varieties where available and start with disease-free transplants.
- 4Rotate for several years — Rotate away from brassicas and control cruciferous weeds; long rotations of several years help but may not fully eliminate the pathogen.
When to escalate
Because clubroot spores persist for many years and resistance-breaking strains exist, confirm the diagnosis and get a soil test and liming recommendation through your local Extension before committing to amendments or resistant varieties. If a bed is confirmed infested, plan long rotations rather than expecting a quick fix.
⚠ Once soil is infested with clubroot, resting spores can remain viable for many years. Preventing spread of contaminated soil is more effective than any rescue treatment.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- NC State Extension — Clubroot of Brassicas — Root galling symptoms, host range, favored by wet acidic soils at 64-77 F, resistant cultivars and multi-year rotation as management