Clubroot in Brassicas: Prevention, Treatment, and Soil Solarization

Clubroot (Plasmodiophora brassicae) persists 7–10 years in soil. Rotation alone is too slow; combine multiple strategies.

Chemical Treatment (Only Option)

Quintozene (Terraclor) 75% WP—drench transplant holes per label. Limited availability; search online. Not organic.

Organic Suppression

• Lime aggressively: pH 7.2–7.5 inhibits (not kills) pathogen. 10–15 lbs/100 sq ft annually × 3 years.
• Solarization: Clear plastic, 6–8 weeks summer heat. Kills pathogen in top 6–12 inches.
• Resistant varieties: 'Kilaton', 'Kilaxy', 'Clapton' (cabbage); 'Crispus' (Brussels sprouts).
• Clean transplants: Start in sterile mix. Never bring in outside plants.
• Sanitation: Clean tools/boots between beds. No composting infected roots.

Integrated 3-Year Plan

Year 1: Solarize bed. Lime to 7.5. Plant resistant varieties in sterile transplants.
Year 2: Maintain pH. Rotate to non-brassicas (legumes, alliums).
Year 3: Test pH. Return brassicas with resistant varieties.

Diagnosis Confirmation

Dig stunted plant—swollen, clubbed, distorted roots = clubroot. Send sample to extension lab for certainty.