Clubroot or, to give it it's Latin Name, Plasmodiophora brassicae, is a particularly nasty disease.
It attacks almost all the members of the brassica family which includes plants like Cabbages, Cauliflowers, Sprouts and Wallflowers and many common weeds such as Willow Herb.
The first signs of the disease are usually a yellowing of the leaves although on some varieties this can also be a purple tinge. The plants are stunted and make very poor growth and wilt very easily, particularly in warm weather. When the plants are lifted and examined, the roots will be found to be swollen and deformed.
The disease is soil borne and is spread very easily and soil, once contaminated has been known to carry the spores for 20 years, even in the absence of suitable hosts. Clubroot thrives even more in poorly drained, acid soils, so these conditions should be avoided. Once your ground has the disease, it is very unlikely that you will get rid of it as it can be spread from one area to another via tools plants or even just walking about.
The effects of Clubroot can be minimised though and a crop achieved by taking a few more precautions than normal.
First, ensure that the ground you are using is freely drained and does not hold any excessive water. Dig in as much organic matter as possible.
Keep a careful check on the pH of the soil and keep to the alkaline side by applications of lime.
Always start seeds off in pots or trays using a good quality compost and transplant into Cell trays. Grow the plants on in these trays before planting into the soil. This ensures that the plant has a good size rootball on it to give it a chance of surviving before the disease gets a hold on it.
When transplanting out, use a proprietary Clubroot dip. This is usually either a powder that you mix with water or a ready made paste, depending upon the manufacturer.
When the plants have been harvested, dig the roots up immediately and either burn them or place them in the domestic refuse immediately. Do not compost the roots of Brassicas or leave them lying around as the disease can be spread further.
© copyright 1999, P. A. Owen