Club root is a fungal infection of the roots of brassicas, such as Brussels sprouts, cabbage, cauliflower, turnip and swede, leading to swollen and distorted roots and stunted growth.
What is club root?
Club root is an infection of the roots of brassicas and related plants by Plasmodiophora brassicae, a soil-dwelling micro-organism related to the slime moulds, leading to massive swelling, distortion and severely retarded growth.
It affects Brussels sprouts, cabbages, cauliflowers, turnips, swedes and radishes, and ornamental relatives such as Cheiranthus (wallflowers), Matthiola (stocks), Aubrieta (aubretia) and cabbage-family weeds such as Capsella bursa-pastoris (shepherd’s purse).
Club root can infect whenever the soil is moist and warm, so most new infections occur from mid-summer until late autumn.
Plasmodiophora brassicae is loosely described as a fungus but is in fact more closely related to the slime moulds. It produces resting spores that can contaminate soil for up to 20 years. In the presence of susceptible plant roots, these resting spores germinate and infect the root hairs, causing the distortion. The fungus produces more resting spores in the affected tissue, which eventually rots and releases them back to the soil, ready for the cycle to start over again.