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Clubroot

Quick facts

  • Clubroot is a disease that affects plants in the cabbage family.
  • Plants infected by clubroot are stunted, wilt easily and may have yellowing leaves.
  • Roots of clubroot infected plants are swollen into thick, irregular club shapes.
  • Distribution of clubroot in Minnesota is unknown.
  • Infected plants should be composted or buried on site.

Susceptible plants

Yellowing, dried-up leaves
Plants wilting due to clubroot

All members of the cabbage family (Brassicaceae) are susceptible to clubroot.

  • This includes cabbage, cauliflower, broccoli, Brussels sprouts, kohlrabi, kale, radish, turnips, rutabaga, mustard greens, collard greens, arugula, bok choy and canola.

The clubroot pathogen can infect the roots of some common weeds without causing symptoms.

How to identify clubroot

Two rows of stunted plants
Stunting due to clubroot

Above ground

  • Plants are stunted.
  • Plants wilt with only slight drought stress.
  • Leaves may turn yellow.
  • Young plants may be killed.
  • Older plants fail to produce a harvestable head.

Below ground

  • Roots are swollen and distorted into large clubs.
  • Smaller bulbous galls may be seen on secondary roots, or coming off a large taproot like a turnip.
  • Clubbed roots are firm and light colored early in the season.
  • Roots turn black and decay by the end of the season.

How clubroot spreads and survives

Clubroot is caused by the pathogen Plasmodiophora brassicae.

  • It will not spread on seed, but it can be brought into a garden on infected transplants.
  • The pathogen forms thick walled spores in infected roots.
  • Spores are released into the soil as roots break down and can survive for 20 years.

Clubroot spores can be brought into a new area on infested soil or compost.

  • Tools like tillers and shovels can spread the pathogen if not cleaned after use in infested soils.
  • Spores can be moved short distances on wind strong enough to blow soil particles.

How to manage clubroot

Soil-covered, swollen, club-like roots on pulled-out plants
Swollen, distorted roots caused by clubroot
  • Grow plants from seed or purchase transplants from a reputable supplier.
  • Inspect transplants for symptoms on roots prior to planting.
  • Only add soil or compost that has been heated to kill pathogens.
    • Soil should be treated with steam and compost should reach 148° F while composting.
  • Remove all soil from tools and clean with a 1:9 solution of household bleach in water or with undiluted Lysol (with the active ingredient 0.1% alkyl dimethylbenzyl ammonium saccharinate).

If clubroot is found in the garden

Once clubroot is found at a site, it is likely to be present at that site indefinitely. Heavily infested sites should not be planted with members of the cabbage family but can be used for other crops.

Follow these recommendations to prevent the spread of the pathogen to a new location and reduce the pathogen population to a low enough level to allow for some production:

  • Bury or compost infected plants on site.
  • Remove soil from tools on site and disinfect tools with a 1:9 solution of household bleach in water or with undiluted Lysol (with the active ingredient 0.1% alkyl dimethylbenzyl ammonium saccharinate) before using them at another location.
  • Do not grow any member of the cabbage family at the site for 5-7 years. This will reduce the pathogen population but not completely eliminate it.
  • Remove all weeds during the crop rotation. The pathogen can survive on many weeds.
  • Clubroot resistant varieties of cabbage are available. These varieties will perform best when planted after a period of 5-7 years during which no member of the cabbage family is grown at the infested site.
  • Submit a soil sample to the UMN Soil Testing Laboratory to determine the soil pH of the garden. If the pH is below 7, apply lime to raise the pH to 7.3 -7.5.

Michelle Grabowski, Extension educator

Reviewed in 2019

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