Clubroot

• Plants wilt during the heat of the day and appear to partially recover by evening
• Stunted, yellowish growth that does not respond to watering or fertilizing
• Distorted, club-shaped or gall-like swellings on roots when dug up
• Eventually plants die or produce very little
• Symptoms look like drought stress above ground but the roots tell the story

Plasmodiophora brassicae is a soil-borne pathogen that can persist in the soil for more than 20 years as resting spores. It favors acidic soils (below pH 6.5) and cool, moist conditions. Spores can be spread by water, contaminated soil on tools and boots, and transplants from infected beds. Once clubroot is established in a bed, it is very difficult to eradicate — prevention is far more effective than treatment.

1. 01Raise soil pH to 7.2 or above by liming — clubroot is significantly suppressed at higher pH
2. 02Apply lime to new beds before introducing brassicas
3. 03Do not move soil, transplants, or tools from infected beds to clean areas without cleaning thoroughly
4. 04Rotate brassicas out of infected beds for at least seven years — spores persist a very long time
5. 05Remove and bag all diseased plants and roots — do not compost
6. 06Purchase transplants from reputable sources or start from seed to avoid introducing the pathogen

Clubroot is worth confirming via lab test before taking drastic measures — the root symptoms can occasionally be confused with other root issues. An extension plant pathologist can confirm the diagnosis and advise on the specific pH target most effective in your soil type.

• Clubroot of Brassicas— University of New Hampshire Extension
• Clubroot Management— Penn State Extension