Clubroot of Brassicas | Integrated Pest Management | College of Agriculture, Health and Natural Resources

Clubroot is a serious soilborne disease of brassica crops caused by Plasmodiophora brassicae, a plasmodiophorid protist that produces long-lived resting spores. It affects crops such as cabbage, broccoli, cauliflower, Brussels sprouts, kale, collards, turnips, rutabagas, radishes, mustard greens, and other brassicas. The pathogen is not seedborne, but it is commonly moved in contaminated transplants, soil, water, equipment, tools, and footwear.

Symptoms include stunting, yellowing, and wilting, often worse during warm parts of the day. The diagnostic symptom is swollen, distorted roots or “clubs.” These roots do not absorb water and nutrients normally, and when they decay they release more resting spores into the soil.

Clubroot is favored by cool, wet, acidic soils. Once a field is infested, there is no economical way to eliminate the pathogen. Management depends on prevention, long rotation, pH adjustment, sanitation, drainage, resistant varieties, and labeled at-planting fungicides where appropriate.

Management

Use clean transplants grown in soilless media. Do not reuse contaminated trays, pots, or media. Avoid moving soil from infested to clean fields on equipment, boots, tools, or irrigation water.
For routine brassica production, use at least a 3-year rotation. If clubroot is detected, rotate out of brassicas for 7 years and control brassica weeds and volunteers during that period. Avoid brassica cover crops in infested fields.
Maintain soil pH at 7.0–7.2 where clubroot is a concern. Lime well ahead of planting and incorporate thoroughly. Improve drainage and avoid planting brassicas in cold, wet, compacted soils. Monitor boron where pH is raised, especially on coarse soils.
Where clubroot has been confirmed, labeled at-planting products listed in the New England Vegetable Management Guide include Ranman, Omega 500F, Blocker 4F, and Serenade ASO. These products may help suppress disease but will not eliminate the pathogen. Always follow the current label and confirm state registration before use.
Use clubroot-tolerant varieties where available, and submit suspect plants to a diagnostic lab for confirmation before making long-term management decisions.

By: Shuresh Ghimire, Vegetable Extension Specialist

May 2026

This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

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