By David Marks

RECOGNISING CLUB ROOT

The first signs you will have are plants that look wilted in warm weather, the leaves may have a bluish tinge to them. Typical of this disease is that the plant recover over night and may look OK in the morning only to wilt later on. As the club root progresses the leaves will yellow and the plants will slowly die.

The absolute confirmation of this disease can only be decided by pulling up plants which are suspect and looking at the root system which will be significantly swollen, often with lumps on it. The infected roots are less able to absorb water and nutrients causing the plant above ground to suffer.

Normally at this stage of a pest / disease article we write we would describe the lifecycle to help you understand what is going on and identify any weak areas. But in the case of club root there will be no indications of the problem until it is far too late. The Latin name for this disease is Plasmodiophora Brassicae.

The disease normally spreads in summer and early autumn, at temperatures below 15°C / 59°F the fungus become inactive and the disease stops developing. Wet soil also assists in the development of Club Root.

PREVENTING AND TREATING CLUB ROOT

There are no chemical treatments currently available for club root.

Club Root is a soil borne spore which is easily spread on footwear and gardening tools. It also can exist on plants and their nearby soil so be very wary of accepting small brassica plants from fellow gardeners.

Club Root has a definite preference for slightly acidic soil so applying lime, which makes the soil more alkaline, is definitely recommended – aim to raise the soil pH above 7.2. Lime can easily be bought at almost all garden centres and should be applied to the soil at the rate recommended on the packet. Doing this will significantly reduce the effect of club root if it is already in the soil.

Club root can exist in the soil for up to 15 years so crop rotation will not get rid of it but it will significantly reduce the effects. Some weeds also harbour club root so keep the soil weed free in areas which are resting from growing brassicas.

For those with club root already in the soil raising seedlings in pots for longer than normal will allow a larger root system to develop before it is planted in the ground. This can often allow crops to be raised successfully in infected soil.

There is an old wives tale that a small amount of rhubarb stalk placed in the planting hole will assist in preventing club root but tests have proven that this has no effect.

Some varieties of brassicas show resistance to club root. These include:

• “Kilaton” cabbage
• “Kilaxy” cabbage
• “Lodero” cabbage
• “Clapton” cauliflower
• “Crispus” brussels sprouts
• “Cronos” brussels sprouts

Further reading about Club Root is available from the following sources:

• A very lengthy but informative document about Club Root from Kelly L. Stewart at Edinburgh University. Click here.
• Yara Crop Nutrition
• An article about Club Root in oil seed rape but the same principles apply to other plants. Click here.

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