Clubroot

Clubroot is not the newest bar in town; it is a disease of many fall and winter crops.


Clubroot, or club root, is caused by an imported plant parasite that grows inside of plant cells. This parasite used to be classified as a slime mold, but is now in an entirely different category, called Phytomyxea. This pathogen is called Plasmodiophora brassicae, but don’t let the name scare you off from learning about it. The brassicae part of the name tells you which plants are susceptible: members of the cabbage family. The Plasmodiophora part of the name tells us that these are mouthless, amoeba-like plant parasites.


Which plants are affected by clubroot?

Clubroot occurs in nearly all members of the brassica family. This means that your broccoli, Brussels sprouts, cabbages, cauliflower, radishes, and turnips are susceptible. In addition, alyssum, mustard, nasturtium, and wallflowers, as brassicas, can also become infested with this parasite.

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Roots infected with clubroot show extensive galling (UCANR)

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Symptoms of clubroot

At first, there may not be any aboveground symptoms to clue you in to this problem. Leaves may begin to wilt or look stunted. They may yellow. Of course, those symptoms could be any number of issues: water stress, nematodes, thrips, aphids…it’s a long list But, if you were to dig the plant up and look at its roots, well, that would be a different story altogether. Roots infested with clubroot parasites are covered with galls (ulcerations). They are also distorted and swollen, interfering with the transfer of water and nutrients that keep the plant alive. One look at the roots and you will know that something isn’t right.

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Clubroot on young broccoli (UCANR)

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Controlling clubroot

Once this micro-critter is in your soil, it may never go away completely. Soil solarization is the only sure way to get rid of it, and that only works if the solarization is done properly. Use these tips to reduce the chance of clubroot occurring in your garden:

• ensure proper drainage
• install clean, disease-free plants
• dispose of infected plants in the trash
• sterilize tools after handling diseased plants
• use green manure cautiously, allowing the soil to dry out periodically
• regularly rotate crops so that brassicas are not planted in the same place each year

When it comes to clubroot, prevention is worth the effort.