Clubroot identification & organic treatment
Plasmodiophora brassicae
How to identify clubroot
A soilborne organism (technically a protist, long grouped with fungal diseases) that infects brassica roots and causes grotesque, swollen, club-shaped galls that cripple water and nutrient uptake.
Symptoms
- Stunted, pale, wilting plants especially in the heat of the day
- Pulling a plant reveals swollen, distorted, club-shaped roots instead of normal fibrous roots
- Galls eventually rot and release spores back into the soil
- Wilting resembles drought stress even with adequate soil moisture
Host crops
Cabbage, Broccoli, Cauliflower, Kale, Brussels Sprouts, Turnip, Collards.
How it spreads
Resting spores survive in soil for a decade or more; spread by moving infested soil on tools, boots, transplants, or irrigation runoff, and via infected transplant roots.
Favorable conditions
Acidic, wet, poorly drained soil (pH below 6.8) and warm soil temperatures favor infection and gall development.
Progression
- Root hair infection (Contact with resting spores in soil) — Invisible; occurs within days of root contact.
- Gall formation (Weeks later) — Roots swell into distorted clubs.
- Above-ground symptoms (As galls impair uptake) — Stunting and daytime wilting appear.
- Gall decay (End of season) — Galls rot, releasing millions of new resting spores into soil.
Organic treatment for clubroot
- 1. Remove and destroy infected plants and roots · medium effort
Pull the whole plant including all root galls and bag it; never compost clubroot-infected material.
When: As soon as identified
- 2. Raise soil pH · medium effort
Lime the bed to bring pH to 7.2 or above; the pathogen struggles in alkaline soil.
When: Season before replanting brassicas
- 3. Improve drainage · medium effort
Build raised beds or add organic matter so soil doesn't stay waterlogged.
When: Bed prep
Prevention
- Rotate brassicas out of infested ground for 5-7+ years; spores are extremely long-lived.
- Sanitize tools and boots between beds; don't move infested soil.
- Buy or start transplants in clean, soilless mix rather than garden soil.
- Control brassica weeds (wild mustard, shepherd's purse) that also host the pathogen.
Easy to confuse with
Cabbage maggot damage (tunneling in roots, not solid swollen galls), Drought stress (no root galls on inspection).