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 plant cells. It 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: the cabbage family. The Plasmodiophora part of the name tells us these are mouthless, amoeba-like plant parasites.

Which plants are affected by clubroot?

Clubroot occurs in nearly all members of the brassica family, including broccoli, Brussels sprouts, cabbages, cauliflower, radishes, and turnips are susceptible. Alyssum, mustard, nasturtium, and wallflowers can also become infected.

Plant roots showing symptoms of club root (David B. Langston, USDA Forest Service) CC BY 3.0

Symptoms of clubroot

At first, there may not be any aboveground symptoms to clue you into this problem. Leaves may begin to wilt or look stunted. They may turn 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, that would be a different story altogether. 

Infected roots are covered with sores (galls). These roots are distorted and swollen, interfering with the transfer of water and nutrients that keep the plant alive. One look at those roots, and you know something isn’t right,

Controlling clubroot

Once this micro-critter is in your soil, you may never get rid of it without soil solarization. And that is a tricky thing to do properly. Use these tips to reduce the chance of clubroot occurring in your garden in the first place:

• Ensure proper drainage.
• Install clean, disease-free plants.
• Dispose of infected plants in the trash.
• Sanitize tools after handling diseased plants.
• Use green manure cautiously, allowing the soil to dry out periodically.
• Rotate crops regularly.

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