Clubroot Disease of Brassicas, Its Recognition and Control

Clubroot is the most devastating disease to affect all members of the brassica family including Brussels sprout, cabbage, cauliflower, calabrese and swede. This virulent fungal disease persists in the soil for many years (spores can lay dormant for over twenty years). Clubroot is often a major problem on old allotment sites and kitchen gardens which have been cultivated for many years. There is no known cure, but by adopting the following strategies decent crops may still be produced.

Recognizing the Presence of Clubroot

Infected plants wilt during hot days and develop stunted red to purple tops.When lifted the roots will be swollen and club-like. In bad infestations the stench from the roots can be horrendous.

How Clubroot Disease Spreads

Clubroot spreads through the soil water and on footwear and garden tools.

Measures to Reduce the Severity of Clubroot

Despite there being no cure measures can be taken to reduce the severity of the damage caused:-

• Improving the drainage of heavy soil by making raised beds and incorporating organic matter in the form of garden compost or well-rotted farmyard manure helps enormously.
• Raising the pH to 7.0 or 7.5 by applying garden lime and thereby making the soil more alkaline is another worthwhile tactic. Putting two good handfuls of lime into each hole and watering the hole before planting may lessen the impact of this disease.
• Growing seedlings in 9cm (at least this big) pots of sterilized compost (growing medium) means a strong root system is in place at planting-out time, this ensures the plants are mature before the disease gets a grip.
• Some gardeners go to the trouble and expense of taking out a large hole for each plant and replacing this with sterilized loam every time they plant their brassicas.

Brassicas Which are Resistant to Clubroot

The development of some brassicas which show resistance to this virulent fungal disease is the most significant breakthrough in the fight to combat the debilitating effects of clubroot. Resistant strains include the following:-

• Swede ‘Invitation’
• Calabrese ‘Trixie’
• Cabbage ‘Kilaxy F1’ and the larger Cabbage ‘Kilaton F1’ are both high yielding autumn/winter ballhead varieties of cabbage which show incredible resistance to clubroot.
• Cauliflower ‘Clapton F1’ matures in summer and autumn producing large white heads. Plants show a very high resistance to clubroot.
• Brussels Sprout ‘Crispus F1’ is the latest addition to the clubroot resistant brassica stable. If it proves to be as good as the cabbage and cauliflower resistant varieties its future is assured.

Learn to Live With Clubroot

Where clubroot disease is present in the soil it can not be eliminated, but the gardener by making raised beds to improve the drainage, applying organic matter as well as lime to raise the pH, and raising young plants in pots is able to reduce its impact and grow reasonable crops. The development of more resistant varieties for all types of brassicas holds out real hope for vegetable growers everywhere.