Clubroot is an infection that affects brassicas, leading to massively swollen and distorted roots with poor growth. Although there is no chemical control to kill off clubroot, there are preventative measures growers can take.
Brussels sprouts, cabbages, cauliflowers, turnips, swedes, kale, calabrese (broccoli) and radishes are all susceptible to attack, as are ornamental relatives such as Cheiranthus (wallflowers), Matthiola (stocks) and Aubrieta.
A soil-dwelling micro-organism, Plasmodiophora brassicae, related to slime moulds is the culprit. It produces spores that can contaminate soil for up to 20 years, so prevention is essential to ensure you dont suffer with clubroot.
If susceptible plant roots are near, the dormant spores germinate and infect the root hairs, causing the distortion. The fungus produces more spores in the affected tissue, which rots and releases them back to the soil.
Most new infections happen from midsummer until late autumn, when the soil is warm and moist.
Symptoms Of Clubroot Disease
Stunted growth and purple-tinged foliage.
Wilting in hot weather, which may recover in wet conditions.
The root system becomes massively swollen and distorted, with a loss of fine root hairs, so the plant can’t take up enough water or nutrients.
Growth is stunted and yields are severely reduced.
Badly affected plants die.
How To Reduce The Chances Of A Clubroot Attack
Even though there is no chemical control, there are several things gardeners can do to prevent infection:
If you buy plants, make sure they come from a club root-free source.
Don’t use plants from other gardeners, whose plants may be infected without their knowledge.
If you know club root spores are present, grow plants on in modules and pots at least 9cm wide in healthy compost to a larger than normal size before planting out. This way, the plants’ developed root systems will stand a better chance of resisting infection.
Spores can be spread on tools, wheelbarrows and footwear. Clean all equipment with disinfectant - a 1% bleach solution is recommended.
As well as liming the soil, improve drainage to make conditions less likely for infections - making raised beds is a good idea.
Keep an eye out for weeds in the cabbage family which can be infected and spread spores, such as shepherd’s purse, charlock and wild radish.
Grow plants or seeds that show club root resistance - try our The Best Club Root Brassica Plant Collection, Club Root Resistant Brassica Seed Collection or Club Root Resistant Brassica Veg Collection.
Individual cultivars showing some level of resistance available from us include Cabbage ‘Kilaton’ F1 and ‘Kilazol’ F1; Cauliflower ‘Clapton’ F1, Brussels sprouts ‘Crispus’ F1 and Calabrese ‘Monclano’ F1.